Research interests
Theoretical and computational physicist working on wave propagation in complex media at the intersection of optics, condensed-matter physics, and wave physics.
- Wave propagation in complex media
- Wave localization phenomena
- Coherent control of wave transport and imaging in turbid media
- Wave diffusion in confined geometries
- Compressive sensing, machine-learning algorithms, and optimization
Computational methods
Honors and recognition
- Co-Editor, Europhysics Letters (EPL), appointed by the European Physical Society (2026–2029)
- CASE Faculty Research Award, College of Arts, Sciences, and Education, Missouri S&T (2025)
- Post-Tenure Review Excellence Award, Missouri S&T (2025)
- Senior Member of Optica (since 2017); Life Member (since 2008)
Education
- 1997 – 2001
- Ph.D. in Physics, The Graduate School and University Center, City University of New York
Thesis: Concept of local polaritons and optical properties of mixed crystals and quantum heterostructures
Adviser: Alexander A. Lisyansky - 1995 – 1997
- M.S. in Physics/Engineering (summa cum laude), Donetsk State University, Ukraine
Thesis: Study of multicomponent systems in the framework of the renormalization group equation - 1992 – 1995
- B.S. in Physics, Donetsk State University, Ukraine
Thesis: Application of Kadanoff–Baym kinetic equations to calculation of electro-conductivity in disordered systems
Professional appointments
- 2021 – present
- Full Professor, Department of Physics, Missouri S&T
- Fall 2022
- Visiting Researcher, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- 2014 – 2021
- Associate Professor, Department of Physics, Missouri S&T
- Fall 2017
- Research Fellow in Residence, Institute for Computational and Experimental Research in Mathematics (ICERM), Brown University
- 2008 – 2014
- Assistant Professor, Department of Physics, Missouri S&T
- 2005 – 2008
- Research Assistant Professor, Department of Physics, Missouri S&T
- 2003 – 2005
- Research Associate, Department of Physics & Astronomy, Northwestern University
- 2001 – 2003
- Postdoctoral Research Fellow, Department of Physics & Astronomy, Northwestern University
- 2000 – 2001
- Adjunct Lecturer, Queensborough Community College, CUNY
- 1997 – 2001
- Research Assistant / Teaching Assistant, Queens College, CUNY
Patent
- P. Jara, A. Yamilov, "Wave Field Compression Using Fourier Domain Shell Masking," U.S. Provisional Patent Application, filed March 2026.
Publications
Citation summary (Google Scholar, April 2026): 3,491 citations, h-index 30, i10-index 63. Latest preprints on arXiv.
- P. Jara, A. Yamilov, submitted (2026), arXiv:2604.17617
Abstract
Advances in computational methods have made full-wave simulations in large disordered media increasingly feasible, but the resulting field data, scaling with the cube of the ratio of system size to wavelength, creates a severe storage and post-processing bottleneck. Generic compression methods are sample-specific and preclude operations on compressed data. We introduce OSCAR (On-Shell Compression And Reconstruction), a physics-based lossy compression scheme for weakly scattering media. OSCAR exploits the universal confinement of the Fourier representation of wave fields to a thin dispersion shell, a direct consequence of wave propagation when the scattering mean free path significantly exceeds the wavelength. The resulting compression ratio reflects two distinct scale separations: on-shell confinement due to weak scattering, and the excess Fourier-space volume introduced by sub-wavelength discretization of the scatterers. Crucially, second-order quantities such as intensity, correlations, and (optical) sensitivity can be computed via convolution entirely in compressed space and remain accurate even when individual field reconstruction incurs appreciable error, because coherent interference between independently compressed fields is preserved. Numerical simulations of electromagnetic waves in 2D and 3D confirm compression ratios up to ~380x with sub-percent field error, enabling routine ensemble studies at scales relevant to biomedical optics, seismology, and underwater acoustics.
- R. E. McIntosh, A. Goetschy, A. Yamilov, N. Bender, H. Yilmaz, H. Cao, submitted (2025), arXiv:2509.10646
Abstract
Time-reversal symmetry allows waves to retrace their paths through complex media and refocus at their origin. However, incomplete capture and reversal of scattered waves often limits pulse re-compression. We address this challenge for spatially extended sources by introducing a generalized time-reversal framework, which identifies the optimal source pattern as the one that maximizes the energy of the waves that are captured and reversed. In a two-dimensional diffusive waveguide, we reconstruct the time-reversed wavefront corresponding to this optimal source using spatio-spectral shaping, leading to a 35-fold enhancement in peak transmitted power compared to an unmodulated pulse. Internal spatio-temporal measurements reveal a "loading and firing" process, in which energy accumulates within the medium and then is released abruptly. Moreover, time-reversing this burst enables deep energy delivery into the scattering medium. Generalized time-reversal opens new possibilities for short-pulse control in strongly-scattering media, with applications ranging from optogenetics to random laser amplification.
- P. Jara, A. Goetschy, H. Cao, A. Yamilov, Phys. Rev. Appl. 24, 054027 (2025)
Abstract
Imaging techniques such as functional near-infrared spectroscopy and diffuse optical tomography (DOT) achieve deep, noninvasive sensing in turbid media; however, they are constrained by the photon budget, as most of the injected light is lost to scattering before reaching the detector. Wavefront shaping (WFS) can enhance signal strength via interference at specific locations within scattering media, enhancing light-matter interactions and potentially extending the penetration depth of these techniques. Interpretation of the resulting measurements relies on knowing the optical sensitivity—the relationship between changes in the detected signals and perturbations at a specific location inside the medium; however, conventional diffusion-based sensitivity models rely on assumptions that become invalid under coherent illumination. In this work, we develop a microscopic theory for optical sensitivity that captures the inherent interference effects that diffusion theory necessarily neglects. We show analytically that, under disorder averaging with random illumination, the microscopic and diffusive descriptions coincide. Beyond this limit, our framework identifies WFS strategies that enhance sensitivity. We demonstrate that the input state obtained through phase conjugation at a given point inside the system leads to the largest enhancement of optical sensitivity but requires an input wavefront that depends on the target position. In sharp contrast, the maximum remission eigenchannel, corresponding to the largest eigenvalue of the monochromatic remission matrix, leads to a global enhancement of the sensitivity map with a fixed input wavefront. This global enhancement equals the remission enhancement and preserves the spatial distribution of the sensitivity, making it compatible with existing DOT reconstruction algorithms. Our results, validated through extensive numerical simulations, establish the theoretical foundation for integrating wavefront control with diffuse optical imaging, enabling deeper tissue penetration through improved signal strength in biomedical applications.
- R. E. McIntosh, A. Goetschy, N. Bender, A. Yamilov, C. W. Hsu, H. Yilmaz, H. Cao, Phys. Rev. B 111, 144202 (2025)
Abstract
The maximum deposition eigenchannel provides the largest possible power delivery to a target region inside a diffusive medium by optimizing the incident wavefront of a monochromatic beam. It originates from constructive interference of scattered waves, which is frequency sensitive. We investigate the spectral width of maximum deposition eigenchannels over a range of target depths using numerical simulations of a 2D diffusive system. Compared to tight focusing into the system, power deposition to an extended region is more sensitive to frequency detuning. The spectral width of enhanced delivery to a large target displays a rather weak, non-monotonic variation with target depth, in contrast to a sharp drop of focusing bandwidth with depth. While the maximum enhancement of power deposited within a diffusive system can exceed that of power transmitted through it, this comes at the cost of a narrower spectral width. We investigate the narrower deposition width in terms of the constructive interference of transmission eigenchannels within the target. We further observe that the spatial field distribution inside the target region decorrelates slower with spectral detuning than power decay of the maximum deposition eigenchannel. Additionally, absorption increases the spectral width of deposition eigenchannels, but the depth dependence remains qualitatively identical to that without absorption. These findings hold for any diffusive waves, including electromagnetic waves, acoustic waves, pressure waves, mesoscopic electrons, and cold atoms.
- A. Yamilov, S. E. Skipetrov, H. Cao, Phys. Rev. Lett. 134, 046302 (2025)
Abstract
We study Anderson transition for light in three dimensions by performing large-scale simulations of electromagnetic wave transport in disordered ensembles of perfect-electric-conducting spatially over-lapping spheres. A mobility edge that separates diffusive transport and Anderson localization is identified, revealing a sharp transition from diffusion to localization for light. Critical behavior in the vicinity of the mobility edge is well described by a single-parameter scaling law. The critical exponent is found to be consistent with the value known for the Anderson transition of the orthogonal universality class. Statistical distribution of total transmission at the mobility edge is described without any fit parameter by the diagrammatic perturbation theory originally developed for scalar wave diffusion, but notable deviation from the theory is found when Anderson localization sets in. Press coverage: APS Physics
- L. Shaughnessy, R. E. McIntosh, A. Goetschy, C. W. Hsu, N. Bender, H. Yilmaz, A. Yamilov, H. Cao, Phys. Rev. Lett. 133, 146901 (2024)
Abstract
Wavefront shaping allows focusing light through or inside strongly scattering media, but the background intensity also increases due to long-range correlations, reducing the target's contrast. By manipulating non-local intensity correlations of scattered waves in a disordered system with input wavefront shaping, we create high-contrast patterns behind strongly scattering media and targeted energy delivery into a diffusive system with minimal change in the surrounding intensity. These are achieved by introducing the contrast operator and the difference operator, and utilizing their eigenstates to maximize the target-to-background intensity contrast and energy difference. This work opens the door to coherent control of non-local effects in wave transport for practical applications.
- R. McIntosh, A. Goetschy, N. Bender, A. Yamilov, C. W. Hsu, H. Yilmaz, H. Cao, Nat. Phot. 18, 744 (2024)
Abstract
Wavefront shaping enables targeted delivery of coherent light into random-scattering media, such as biological tissue, by constructive interference of scattered waves. However, broadband waves have short coherence times, weakening the interference effect. Here, we introduce a broadband deposition matrix that identifies a single input wavefront that maximizes the broadband energy delivered to an extended target deep inside a diffusive system. We experimentally demonstrate that long-range spatial and spectral correlations result in a six-fold energy enhancement for targets containing more than 1500 speckle grains and located at a depth of up to ten transport mean free paths, even when the coherence time is an order of magnitude shorter than the diffusion dwell time of light in the scattering sample. In the broadband (fast decoherence) limit, enhancement of energy delivery to extended targets becomes nearly independent of the target depth and dissipation. Our experiments, numerical simulations, and analytic theory establish the fundamental limit for broadband energy delivery deep into a diffusive system, which has important consequences for practical applications.
- P. Jara-Palacios, H.-C. Lin, C.-W. Hsu, H.Cao, A. Yamilov, 2023 International Applied Computational Electromagnetics Society Symposium, ACES-Monterey (2023)
Abstract
Waves remitted from a scattering medium carry information that can be used for non-invasive imaging and sensing. Such techniques are usually limited by a low photon budget. Recent progress in optical wavefront shaping has enabled coherent control with an order-of-magnitude enhancement of remission [1]. This experimental study necessitated increasingly demanding numerical simulations. Extending this line of research requires more sophisticated computational techniques capable of simulating multiple instances of even larger systems. Here, we demonstrate that remission geometry can be efficiently simulated using a novel open-source software package [2] Maxwell's Equations Solver with Thousands of Inputs (MESTI). To verify its numerical performance, several simulations and comparisons with the method used previously are presented. Excellent qualitative and quantitative agreement with previous results is obtained. Additionally, orders of magnitude improvement in the computational performance of MESTI is observed. This opens the path to computational modeling of spectral and temporal remission from large scattering systems. [](https://arxiv.org/search/?searchtype=author&query=Yamilov%2C+A)
- A. Yamilov, S. E. Skipetrov, T. W. Hughes, M. Minkov, Z. Yu, H. Cao, Nat. Phys. 19, 1308–1313 (2023)
Abstract
Anderson localization marks a halt of diffusive wave propagation in disordered systems. Despite extensive studies over the past 40 years, Anderson localization of light in three dimensions has remained elusive, leading to the question of its very existence. Recent orders-of-magnitude speed-up of finite-difference time-domain calculations allows us to conduct brute-force numerical simulations of light transport in fully disordered 3D systems with unprecedented dimension and refractive index contrast. We demonstrate three-dimensional localization of vector electromagnetic waves in random packings of metallic spheres, in sharp contrast to the absence of localization for dielectric spheres with a refractive index contrast up to 10. Our work opens a wide range of avenues in both fundamental research related to Anderson localization and potential applications using 3D localized light. Data downloads: Scholarsmine Code: Flexcompute Press coverage: Nature Physics News and Views, Missouri S&T, Optics&Photonics News (Optica), Laser Focus World, Yale, Flexcompute
- N. Bender, A. Goetschy, C. W. Hsu, H. Yilmaz, P. Jara Palacios, A. Yamilov, H. Cao, PNAS 119, 2207089119 (2022)
Abstract
From the earth's crust to the human brain, remitted waves are used for sensing and imaging in a diverse range of diffusive media. Separating the source and detector increases the penetration depth of remitted light, yet rapidly decreases the signal strength, leading to a poor signal-to-noise ratio. Here, we experimentally and numerically show that wavefront shaping a laser beam incident on a diffusive sample enables an order of magnitude remission enhancement, with a penetration depth of up to 10 transport mean free paths. We develop a theoretical model which predicts the maximal-remission enhancement. Our analysis reveals a significant improvement in the sensitivity of remitted waves, to local changes of absorption deep inside diffusive media. This work illustrates the potential of coherent wavefront control for non-invasive diffuse-wave imaging applications, such as diffuse optical tomography and functional near-infrared spectroscopy.
- A. Yamilov, N. Bender, and H. Cao, Opt. Lett. 47, 4889-4892 (2022)
Abstract
In a random-scattering system, the deposition matrix maps the incident wavefront onto the internal field distribution across a target volume. The corresponding eigenchannels have been used to enhance the wave energy delivered to the target. Here, we find the sum rules for the eigenvalues and eigenchannels of the deposition matrix in any system geometry: including two- and three-dimensional scattering systems, as well as narrow waveguides and wide slabs. We derive a number of constraints on the eigenchannel intensity distributions inside the system as well as the corresponding eigenvalues. Our results are general and applicable to random systems of arbitrary scattering strength as well as different types of waves including electromagnetic waves, acoustic waves, and matter waves.
- S. Gigan, O. Katz, H. B. de Aguiar, E. R. Andresen, A. A., J. Bertolotti, E. Bossy, D. Bouchet, J. Brake, S. Brasselet, Y. Bromberg, H. Cao, T. Chaigne, Z. Cheng, W. Choi, T. Cizmar, M. Cui, V. R. Curtis, H. Defienne, M. Hofer, R. Horisaki, R. Horstmeyer, N. Ji, A. K. LaViolette, J. Mertz, C. Moser, A. P. Mosk, N. C. Pegard, R. Piestun, S. Popoff, D. B. Phillips, D. Psaltis, B. Rahmani, H. Rigneault, S. Rotter, L. Tian, I. M. Vellekoop, L. Waller, L. Wang, T. Weber, S. Xiao, C. Xu, A. Yamilov, C. Yang, H. Yilmaz, J. Phys. Photonics 4, 042501 (2022)
Abstract
The last decade has seen the development of a wide set of tools, such as wavefront shaping, computational or fundamental methods, that allow us to understand and control light propagation in a complex medium, such as biological tissues or multimode fibers. A vibrant and diverse community is now working in this field, which has revolutionized the prospect of diffraction-limited imaging at depth in tissues. This roadmap highlights several key aspects of this fast developing field, and some of the challenges and opportunities ahead.
- N. Bender, A. Yamilov, A. Goetschy, H. Yilmaz, C. W. Hsu, H. Cao, Nat. Phys. 18, 309-315 (2022) (arXiv version)
Abstract
A grand challenge in fundamental physics and practical applications is overcoming wave diffusion to deposit energy into a target region deep inside a diffusive system. While it is known that coherently controlling the incident wavefront allows diffraction-limited focusing inside a diffusive system, in many applications targets are significantly larger than such a focus and the maximum deliverable energy remains unknown. Here, we introduce the "deposition matrix", which maps an input wavefront to its internal field distribution, and theoretically predict the ultimate limitations on energy deposition at any depth. For example, the maximum obtainable energy enhancement occurs at 3/4 a diffusive system's thickness: regardless of its scattering strength. Experimentally we measure the deposition matrix and excite its eigenstates to enhance/suppress the energy within an extended target region. Our theoretical analysis reveals that such enhancement/suppression results from both selective transmission eigenchannel excitation and constructive/destructive interference among these channels.
- N. Bender, A. Yamilov, H. Yilmaz, H. Cao, Phys. Rev. Lett. 125, 165901 (2020)
Abstract
Selective excitation of a diffusive system’s transmission eigenchannels enables manipulation of its internal energy distribution. The fluctuations and correlations of the eigenchannels’ spatial profiles, however, remain unexplored so far. Here we show that the depth profiles of high-transmission eigenchannels exhibit low realization-to-realization fluctuations. Furthermore, our experimental and numerical studies reveal the existence of inter-channel correlations, which are significant for low-transmission eigenchannels. Because high-transmission eigenchannels are robust and independent from other eigenchannels, they can reliably deliver energy deep inside turbid media.
- H. Y?lmaz, C. W. Hsu, A. Goetschy, S. Bittner, S. Rotter, A. Yamilov, H. Cao, Phys. Rev. Lett. 123, 203901 (2019)
Abstract
The optical memory effect has emerged as a powerful tool for imaging through multiple-scattering media; however, the finite angular range of the memory effect limits the field of view. Here, we demonstrate experimentally that selective coupling of incident light into a high-transmission channel increases the angular memory-effect range. This enhancement is attributed to the robustness of the high-transmission channels against such perturbations as sample tilt or wavefront tilt. Our work shows that the high-transmission channels provide an enhanced field of view for memory effect-based imaging through diffusive media.
- M. Koirala, R. Sarma,H. Cao, and A. Yamilov, Phys. Rev. B 100, 064203 (2019)
Abstract
We demonstrate a possibility of using geometry to deterministically control nonlocal correlation of waves undergoing mesoscopic transport through a disordered waveguide. In case of nondissipative medium, we find an explicit relationship between correlation and the shape of the system. Inverting this relationship, we realize inverse design: we obtain specific waveguide shape that leads to a predetermined nonlocal correlation. The proposed technique offers an approach to coherent control of wave propagation in random media that is complementary to wave-front shaping.
- H. Yilmaz, C. W. Hsu, A. Yamilov, H. Cao, Nat. Phot. 13, 352 (2019)
Abstract
Transmission eigenchannels are building blocks of coherent wave transport in diffusive media, and selective excitation of individual eigenchannels can lead to diverse transport behaviour. An essential yet poorly understood property is the transverse spatial profile of each eigenchannel, which is relevant for the associated energy density and critical for coupling light into and out of it. Here, we discover that the transmission eigenchannels of a disordered slab possess exponentially localized incident and outgoing profiles, even in the diffusive regime far from Anderson localization. Such transverse localization arises from a combination of reciprocity, local coupling of spatial modes and non-local correlations of scattered waves. Experimentally, we observe signatures of such localization even with finite illumination area. The transverse localization of high-transmission channels enhances optical energy densities inside turbid media, which will be important for light–matter interactions and imaging applications.
- A. G. Yamilov, R. Sarma, V. V. Yakovlev, and H. Cao, Opt. Lett. 43, 2189-2192 (2018)
Abstract
We demonstrate that interplay between absorption and scattering in a dielectric medium with a microscopic pore gives rise to eigenchannels concentrated in the pore. Such a circumvention of attenuation leads to high transmission. By exciting such eigenchannels in a disordered nanophotonic system with a wavefront shaping technique, we experimentally confirm enhanced injection at depths exceeding the limiting length scales set by scattering, absorption, and diffraction.
- [](2017pnas.pdf)Enhanced optical coupling and Raman scattering via microscopic interface engineeringJ. V. Thompson, B. H. Hokr, W. Kim, C. W. Ballmann, B. Applegate, J. Jo, A. Yamilov, H. Cao, M. O. Scully, and V. V. Yakovlev, Appl. Phys. Lett. 111, 201105 (2017)
Abstract
Spontaneous Raman scattering is an extremely powerful tool for the remote detection and identification of various chemical materials. However, when those materials are contained within strongly scattering or turbid media, as is the case in many biological and security related systems, the sensitivity and range of Raman signal generation and detection is severely limited. Here, we demonstrate that through microscopic engineering of the optical interface, the optical coupling of light into a turbid material can be substantially enhanced. This improved coupling facilitates the enhancement of the Raman scattering signal generated by molecules within the medium. In particular, we detect at least two-orders of magnitude more spontaneous Raman scattering from a sample when the pump laser light is focused into a microscopic hole in the surface of the sample. Because this approach enhances both the interaction time and interaction region of the laser light within the material, its use will greatly improve the range and sensitivity of many spectroscopic techniques, including Raman scattering and fluorescence emission detection, inside highly scattering environments.
- M. Koirala, R. Sarma, H. Cao, A. Yamilov, Phys. Rev. B 96, 054209 (2017)
Abstract
Light-matter interactions inside a turbid medium can be controlled by tailoring the spatial distribution of energy density throughout the system. Wavefront shaping allows selective coupling of incident light to different transmission eigenchannels, producing dramatically different spatial intensity profiles. In contrast to the density of transmission eigenvalues that is dictated by the universal bimodal distribution, the spatial structures of the eigenchannels are not universal and depend on the confinement geometry of the system. Here, we develop and verify a model for the transmission eigenchannel with the corresponding eigenvalue close to unity. By projecting the original problem of two-dimensional diffusion in a homogeneous scattering medium onto a one-dimensional inhomogeneous diffusion, we obtain an analytical expression relating the intensity profile to the shape of the confining waveguide. Inverting this relationship enables the inverse design of the waveguide shape to achieve the desired energy distribution for the perfectly transmitting eigenchannel. Our approach also allows to predict the intensity profile of such a channel in a disordered slab with open boundaries, pointing to the possibility of controllable delivery of light to different depths with local illumination.
- J. V. Thompson, B. H. Hokr, W. Kim, C. W. Ballmann, B. Applegate, J. Jo, A. Yamilov, H. Cao, M. O. Scully, and V. V. Yakovlev, PNAS 114, 7941 (2017)
Abstract
There are many optical detection and sensing methods used today that provide powerful ways to diagnose, characterize, and study materials. For example, the measurement of spontaneous Raman scattering allows for remote detection and identification of chemicals. Many other optical techniques provide unique solutions to learn about biological, chemical, and even structural systems. However, when these systems exist in a highly scattering or turbid medium, the optical scattering effects reduce the effectiveness of these methods. In this article, we demonstrate a method to engineer the geometry of the optical interface of a turbid medium, thereby drastically enhancing the coupling efficiency of light into the material. This enhanced optical coupling means that light incident on the material will penetrate deeper into (and through) the medium. It also means that light thus injected into the material will have an enhanced interaction time with particles contained within the material. These results show that, by using the multiple scattering of light in a turbid medium, enhanced light–matter interaction can be achieved; this has a direct impact on spectroscopic methods such as Raman scattering and fluorescence detection in highly scattering regimes. Furthermore, the enhanced penetration depth achieved by this method will directly impact optical techniques that have previously been limited by the inability to deposit sufficient amounts of optical energy below or through highly scattering layers.
- A. Niemeyer, F. Mayer, A. Naber, M. Koirala, A. Yamilov, M. Wegener, Opt. Lett. 42, 1998 (2017)
Abstract
Within the range of validity of the stationary diffusion equation, an ideal diffusive-light invisibility cloak can make an arbitrary macroscopic object hidden inside of the cloak indistinguishable from the surroundings for all colors, polarizations, and directions of incident visible light. However, the diffusion equation for light is an approximation which becomes exact only in the limit of small coherence length. Thus, one expects that the cloak can be revealed by illumination with coherent light. The experiments presented here show that the cloaks are robust in the limit of large coherence length but can be revealed by analysis of the speckle patterns under illumination with partially coherent light. Experiments on cylindrical core-shell cloaks and corresponding theory are in good agreement.
- R. Sarma, A. Yamilov, H. Cao, Appl. Phys. Lett. 110, 021103 (2017)
Abstract
We enhanced the total transmission of light through a disordered waveguide with spatially inhomogeneous scattering and loss by shaping the incident wavefront of a laser beam. Using an on-chip tapered lead, we were able to access all input modes in the waveguide with a spatial light modulator. The adaptive wavefront shaping resulted in selective coupling of input light to high transmission channels, which bypassed the regions of higher scattering and loss in the waveguide. Spatial inhomogeneity in scattering and loss leads to the modification of the spatial structures of transmission eigenchannels, allowing wavefront shaping to redirect the energy flux to circumvent regions of higher scattering and loss and thereby enhancing the energy transported through the system. This work demonstrates the power of wavefront shaping in coherent control of light transport in inhomogeneous scattering media, which are common in real applications.
- R. Sarma, A. Yamilov, S. Petrenko, Y. Bromberg, H. Cao, Phys. Rev. Lett. 117, 086803 (2016)
Abstract
We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides an on-chip platform for controlling light-matter interactions in turbid media.
- M. Koirala and A. Yamilov, Opt. Lett. 41, 3860 (2016)
Abstract
We propose a scheme to detect the diffusive cloak proposed by Schittny et al. [Science 345, 427 (2014).]. We exploit the fact that diffusion of light is an approximation that disregards wave interference. The long-range contribution to intensity correlation is sensitive to the locations of path crossings and the interference inside the medium, allowing one to detect the size and position, including the depth, of the diffusive cloak. Our results also suggest that it is possible to separately manipulate the first- and the second-order statistics of wave propagation in turbid media.
- A. Yamilov, S. Petrenko, R. Sarma, H. Cao, Phys. Rev. B 93, 100201(R) (2016)
Abstract
The universal bimodal distribution of transmission eigenvalues in lossless diffusive systems underpins such celebrated phenomena as universal conductance fluctuations, quantum shot noise in condensed matter physics, and enhanced transmission in optics and acoustics. Here, we show that in the presence of absorption, the density of the transmission eigenvalues depends on the confinement geometry of the scattering media. Furthermore, in an asymmetric waveguide, the densities of the reflection and absorption eigenvalues also depend on the side from which the waves are incident.With increasing absorption, the density of absorption eigenvalues transforms from a single-peak to a double-peak function. Our findings open an additional avenue for coherent control of wave transmission, reflection, and absorption in random media.
- R. Sarma, A. Yamilov, S. F. Liew, M. Guy, H. Cao, Phys. Rev. B 92, 214206 (2015)
Abstract
While controlling particle diffusion in a confined geometry is a popular approach taken by both natural and artificial systems, it has not been widely adopted for controlling light transport in random media, where wave interference effects play a critical role. The transmission eigenchannels determine not only light propagation through the disordered system but also the energy concentrated inside. Here, we propose and demonstrate an effective approach to modify these channels, whose structures are considered to be universal in conventional diffusive waveguides. By adjusting the waveguide geometry, we are able to alter the spatial profiles of the transmission eigenchannels significantly and deterministically from the universal ones. In addition, evanescent channels may be converted to propagating channels by gradually increasing the waveguide cross-section. Our approach allows to control not only the transmitted and reflected light, but also the depth profile of energy density inside the scattering system. In particular geometries, perfect reflection channels are created, and their large penetration depth into the turbid medium as well as the complete return of probe light to the input end would greatly benefit sensing and imaging applications. Absorption along with geometry can be further employed for tuning the decay length of energy flux inside the random system, which cannot be achieved in a common waveguide with uniform cross-section. Our approach relies solely on confined geometry and does not require any modification of intrinsic disorder, thus it is applicable to a variety of systems and also to other types of waves.
- R. Sarma, A. Yamilov, P. Neupane, H. Cao, Phys. Rev. B 92, 180203(R) (2015)
Abstract
We demonstrate an effective approach of modifying the long-range spatial correlation for light propagating inside random photonic waveguides by varying the shape of the waveguide. The functional form of spatial correlation is no longer universal in the regime of diffusive transport and becomes shape dependent due to the nonlocal nature of wave propagation. The spatial dependence of the correlation may become asymmetric for light incident from opposite ends of the waveguide. This work opens the door to control nonlocal effects in mesoscopic transport of waves by tailoring the geometry of random systems.
- P. Neupane, A. Yamilov, Phys. Rev. B 92, 014207 (2015)
Abstract
In this work we show analytically and numerically that the localized regime of wave transport can be modeled as position-dependent diffusion with a diffusion coefficient that retains the memory of the source location. The dependence on the source diminishes when absorption is introduced.
- M. Koirala, A. Yamilov, A. Basiri, Y. Bromberg, H. Cao, T. Kottos, New J. Phys. 17, 013003 (2015)
Abstract
We introduce a class of critical states which are embedded in the continuum (CSC) of a one-dimensional optical waveguide array with one non-Hermitian defect. These states are on the verge of being fractal and have real propagation constants. They emerge at a phase transition which is driven by the imaginary refractive index of the defective waveguide and it is accompanied by a mode segregation which reveals analogies with the Dicke super-radiance. Below this point the states are extended while above it they evolve to exponentially localized modes. An addition of a background gain or loss can turn these localized states into bound states in the continuum.
- A. Basiri, Y. Bromberg, A. Yamilov, H. Cao, and T. Kottos, Phys. Rev. A 90, 043815 (2014)
Abstract
We show the emergence of light localization in arrays of coupled optical waveguides with randomness only in the imaginary part of their refractive index and develop a one-parameter scaling theory for the normalized participation number of Floquet-Bloch modes. This localization introduces a different length scale in the decay of the autocorrelation function of a paraxial beam propagation. Our results are relevant to a vast family of systems with randomness in the dissipative part of their impedance spatial profile.
- R. Sarma, T. Golubev, A. Yamilov, and H. Cao, Appl. Phys. Lett. 105, 041104 (2014)
Abstract
We control the diffusion of light in a disordered photonic waveguide by modulating the waveguide geometry. In a single waveguide of varying cross-section, the diffusion coefficient changes spatially in two dimensions due to localization effects. The intensity distribution inside the waveguide agrees with the prediction of the self-consistent theory of localization. Our work shows that wave diffusion can be efficiently manipulated without modifying the structural disorder.
- R. Sarma, A. Yamilov, P. Neupane, B. Shapiro, and H. Cao, Phys. Rev. B 90, 014203 (2014)
Abstract
We report the direct observation of the development of long-range spatial intensity correlation and the growth of intensity fluctuations inside random media. We fabricated quasi-two-dimensional disordered photonic structures and probed light transport from a third dimension. Good agreement between experiment and theory is obtained. We were able to manipulate the long-range intensity correlation and intensity fluctuations inside the disordered waveguides by simply varying the waveguide geometry.
- [](http://arxiv.org/pdf/1303.3244v1)Position-dependent diffusion of light in disordered waveguides, (supplementaryinformation is here) A. Yamilov, R. Sarma, B. Redding, B. Payne, H. Noh, and H. Cao, Phys. Rev. Lett. 112, 023904 (2014)
Abstract
We present direct experimental evidence for position-dependent diffusion in open random media. The interference of light in time-reversed paths results in renormalization of the diffusion coefficient, which varies spatially. To probe the wave transport inside the system, we fabricate two-dimensional disordered waveguides and monitor the light intensity from the third dimension. Change the geometry of the system or dissipation limits the size of the loop trajectories, allowing us to control the renormalization of the diffusion coefficient. This work shows the possibility of manipulating wave diffusion via the interplay of localization and dissipation.
- A. Yamilov and B. Payne, Optics Express 21, 11688–11697 (2013)
Abstract
This work presents results of ab-initio simulations of continuous wave transport in disordered absorbing waveguides. Wave interference effects cause deviations from diffusive picture of wave transport and make the diffusion coefficient position- and absorption-dependent. As a consequence, the true limit of a zero diffusion coefficient is never reached in an absorbing random medium of infinite size, instead, the diffusion coefficient saturates at some finite constant value. Transition to this absorption-limited diffusion exhibits a universality which can be captured within the framework of the self-consistent theory (SCT) of localization. The results of this work (i) justify use of SCT in analyses of experiments in localized regime, provided that absorption is not weak; (ii) open the possibility of diffusive description of wave transport in the saturation regime even when localization effects are strong.
- B. Payne, T. Mahler, and A. Yamilov, Waves in Random and Complex Media 23, 43-55 (2013)
Abstract
We employ ab initio simulations of wave transport in disordered waveguides to demonstrate explicitly that although accounting for evanescent channels manifests itself in the renormalization of the transport mean free path, the position dependent diffusion coefficient, as well as distributions of angular transmission, total transmission and conductance, all remain universal.
- S. Herath, N. P. Puente, E.I. Chaikina and A. Yamilov, Optics Express 20, 3620-3632 (2012)
Abstract
This work presents results of ab-initio simulations of continuous wave transport in disordered absorbing waveguides. Wave interference effects cause deviations from diffusive picture of wave transport and make the diffusion coefficient position- and absorption-dependent. As a consequence, the true limit of a zero diffusion coefficient is never reached in an absorbing random medium of infinite size, instead, the diffusion coefficient saturates at some finite constant value. Transition to this absorption-limited diffusion exhibits a universality which can be captured within the framework of the self-consistent theory (SCT) of localization. The results of this work (i) justify use of SCT in analyses of experiments in localized regime, provided that absorption is not weak; (ii) open the possibility of diffusive description of wave transport in the saturation regime even when localization effects are strong.
- A. Yamilov and H. Cao, book chapter in "Optical properties of photonic structures: interplay between order and disorder," ed. by. M. Limonov and R. De La Rue (Taylor & Francis 2012)
Abstract
Light scattering is usually regarded detrimental to optical confinement in conventional lasers. In contrast, in random lasers, the confinement is caused by disorder-induced scattering. In strongly scattering media, the lasing is defined by the high-quality modes of the passive system. Thus, by incorporating and optimizing a degree of order, one can dramatically reduce the threshold of a random laser to the values comparable to those of photonic crystal (PhC) lasers. Unlike the latter, where the optical cavity has to be carefully designed and impeccably fabricated, in disordered systems the modes originate from the structure imperfections unintentionally introduced during the fabrication process. Optical gain selectively amplifies the high-quality modes of the passive system. Consequently, in PhC slab geometry, for example, the in-plane and out-of-plane leakage rates of the lasing modes can become automatically balanced in the presence of disorder. Such self-optimization of optical confinement makes disordered PhC structures a competitive platform for large scale low-cost production of microlasers with fabrication requirements much less stringent than those of PhC lasers with designed cavities.
- N. P. Puente, E.I. Chaikina, S. Herath and A. Yamilov, Appl. Opt. 50, 802 (2011) Highlighted in Spotlight on Optics
Abstract
We present results of experimental and theoretical studies of polarization-resolved light transmission through optical fiber with disorder generated in its germanium-doped core via UV radiation transmitted through a diffuser. In samples longer than a certain characteristic length, the power transmitted with preserved polarization is observed to be distributed over all forward-propagating modes, as evidenced by the Rayleigh negative exponential distribution of the near-field intensity at the output surface of the fiber. Furthermore, the transmitted power becomes also equally distributed over both polarizations. To describe the optical properties of the fibers with the experimentally induced disorder, a theoretical model based on coupled-mode theory is developed. The obtained analytical expression for the correlation function describing spatial properties of the disorder shows that it is highly anisotropic. Our calculation demonstrate that this experimentally controllable anisotropy can lead to suppression of the radiative leakage of the propagating modes, so that intermode coupling becomes the dominant scattering process. The obtained theoretical expressions for the polarization-resolved transmission fit very well with the experimental data, and the information extracted from the fit shows that radiative leakage is indeed small. The reported technique provides an easy way to fabricate different configurations of controlled disorder in optical fibers suitable for such applications as random fiber lasers.
- N. P. Puente, E.I. Chaikina, S. Herath and A. Yamilov, SPIE Proceedings: Specialty Optical Fibers and Their Applications 7839, 78391O-1 (2010)
Abstract
This paper presents results of experimental and theoretical studies of light transmission through optical fibers with disorder generated in its germanium-doped core via UV radiation transmitted through a diffuser. The experimental results on transmission of the radiation of 543 nm wavelength demonstrate the presence of the disorder in the core of the optical fiber – beyond a certain characteristic length, the transmitted power is observed to be distributed over all modes of the fiber. A theoretical model based on coupled mode theory is developed. An analytical expression for the mixing length is obtained and agrees well with the experiment. For long sections of disordered fiber, the experimentally measured distribution of the near-field intensity at the output surface of the fiber is well described by the Rayleigh negative exponential function. This suggests a statistically uniform distribution of the transmitted power over all modes, that agrees with the prediction of the theoretical model. The reported technique provides an easy way to fabricate different configurations of controlled disorder in optical fibers suitable for such applications as random fiber lasers.
- A. Yamilov and B. Payne, J. Mod. Opt. 57, 1916 (2010)
Abstract
Passive quasi-one-dimensional random media are known to exhibit one of the three regimes of transport - ballistic, diffusive or localized - depending on the system size. In contrast, in non-conservative systems, the physical parameter space also includes the gain/absorption length scale. Here, by studying the relationships between the transport mean free path, the localization length, and the gain/absorption length, we enumerate 15 regimes of wave propagation through quasi-one-dimensional random media with gain or absorption. The results are presented graphically in the form of a phase diagram. Of particular experimental importance in an absorbing random medium, we identify three different regimes that bear the signatures of the localized regime of the passive counterpart. We also review the literature and, when possible, assign experimental systems to a particular regime on the diagram.
- B. Payne, J. Andreasen, H. Cao, and A. Yamilov, Phys. Rev. B 82, 104204 (2010)
Abstract
In this work, we investigate a possibility of using the ratio between optical transmission, T, and energy stored inside the system, E, as a quantitative measure of the enhanced mesoscopic corrections to diffusive transport of light through a random medium with gain. We obtain an expression for T/E as a function of amplification strength in the diffusive approximation and show that it does not a have tendency to diverge when the threshold for random lasing is approached, as both T and E do. Furthermore, we find that a change in T/E signifies a change in the electric field distribution inside the random medium. In the localization regime, we also investigate the correlations between transmission and energy stored in the medium with and without amplification. Our results suggest that T/E is a promising parameter which can help characterize the nature of wave transport in random medium with gain.
- B. Payne, A. Yamilov, S. E. Skipetrov, Phys. Rev. B 82, 024205 (2010) arXiv:1005.0013
Abstract
We show that the recently developed self-consistent theory of Anderson localization with a position-dependent diffusion coefficient is in quantitative agreement with the supersymmetry approach up to terms of the order of 1/g0^2 with g0 the dimensionless conductance in the absence of interference effects and with large scale ab initio simulations of the classical wave transport in disordered waveguides, at least for g0~0.5. In the latter case, agreement is found even in the presence of absorption. Our numerical results confirm that in open disordered media, the onset of Anderson localization can be viewed as position-dependent diffusion.
- A. Yamilov and M. Herrera, in "Recent Optical and Photonic Technologies," Ed. by Ki Young Kim, INTEH, (2010) ISBN 978-953-7619-71-8
Abstract
In this chapter we discuss optical properties of dual-periodic photonic (super-)structures. Conventional photonic crystal structures exhibit a periodic modulation of the dielectric constant in one, two or three spatial dimensions.
- B. Payne, H. Cao, and A. Yamilov, Physica B 405, 3012 (2010)
Abstract
Dimensionless conductance for light propagating through a random medium with amplification tends to diverge with an increase of gain.This raises questions on the applicability of the localization criteria based on this quantity. To circumvent this problem, we study the properties of the ratio between the transmission (conductance) and the energy stored in the random medium. We argue that the generalized conductance - conductance normalized by the energy buildup (ratio between energy stored in the medium with gain to that in the passive system) - may be a convenient quantity on which a localization criterion can be built.
- M. Scharrer, H. Noh, X. Wu, M. A. Anderson, A. Yamilov, H. Cao, and R. P. H. Chang, J. Opt. 12, 024007 (2010)
Abstract
We report room temperature lasing in ZnO inverse opal photonic crystals in the near-ultraviolet (UV) frequency range. We observe random lasing due to disorder in the structures when the photonic pseudogaps are located away from the ZnO gain spectrum. Tuning the first GammaL-pseudogap to the gain peak leads to a five-fold reduction in lasing threshold and a frequency shift of the lasing modes due to the enhanced confinement of light.
- Relation between channel and spatial mesoscopic correlations in volume-disordered waveguides,[](http://arxiv.org/abs/0706.1335)A. Yamilov, Phys. Rev. B 78, 045104 (2008)
Abstract
We investigate the relationship between channel and spatial mesoscopic correlations in volume-disordered waveguides. We emphasize the importance of the surface escape function, which describes the distribution of transmitted flux among different channels, and we derive expressions for spatial field and intensity correlation functions directly from the channel ones.
- A. Yamilov, M. R. Herrera and M. F. Bertino, Journal of Optical Society of America B 25, 599-608 (2008)
Abstract
We present analytical and numerical studies of a photonic lattice with short- and long-range harmonic modulations of the refractive index. Such structures can be prepared experimentally with holographic photolithography. In the spectral region of the photonic bandgap of the underlying single-periodic crystal, we observe a series of bands with anomalously small dispersion. The related slow-light effect is attributed to the long-range modulation of the photonic lattice that leads to formation of an array of evanescently coupled high-Q cavities. The band structure of the lattice is studied with several techniques: (i) transfer matrix approach; (ii) an analysis of resonant coupling in the process of band folding; (iii) effective-medium approach based on coupled-mode theory; and (iv) the Bogolyubov–Mitropolsky approach. The latter method, commonly used in the studies of nonlinear oscillators, was employed to investigate the behavior of eigenfunction envelopes and the band structure of the dual-periodic photonic lattice. We show that reliable results can be obtained even in the case of large refractive index modulation.
- R. L. Weaver, O. I Lobkis, and A. Yamilov, J. Acoust. Soc. Am. 122, 3409-18 (2007)
Abstract
Theoretical modeling and laboratory tests are conducted for nonlinear auto-oscillating piezoelectric ultrasonic devices coupled to reverberant elastic bodies. The devices are shown to exhibit behavior familiar from the theory of coupled auto-oscillators. In particular, these spontaneously emitting devices adjust their limit-cycle frequency to the spectrum of the body. It is further shown that the auto-oscillations can be entrained by an applied field; an incident wave at a frequency close to the frequency of the natural limit cycle entrains the oscillator. Special attention is paid to the phase of entrainment. Depending on details, the phase is such that the oscillator can be in a state of stimulated emission: the incident field amplifies the ultrasonic power emitted by the oscillator. These behaviors are essential to eventual design of an ultrasonic system that would consist of a number of such devices all synchronized to their mutual field, a system that would be an analog to a laser. A prototype uaser is constructed.
- X. Wu, J. Andreasen, H. Cao, and A. Yamilov, Journal of Optical Society of America B 24, A26 (2007)
Abstract
We have developed a numerical method based on the transfer matrix to calculate the quasi modes and lasing modes in one-dimensional random systems. Depending on the relative magnitude of the localization length versus the system size, there are two regimes in which the quasi modes are distinct in spatial profile and frequency distribution. In the presence of uniform gain, the lasing modes have one-to-one correspondence to the quasi modes in both regimes. Local excitation may enhance the weight of a mode within the gain region due to local amplification, especially in a weakly scattering system.
- M. F. Bertino, R. R. Gadipalli, L. A. Martin, L. E. Rich, A. Yamilov, B. R. Heckman, N. Leventis, S. Guha, J. Katsoudas, R. Divan and D. C. Mancini, Nanotechnology 18, 315603 (2007)
Abstract
Highly luminescent semiconductor quantum dots have been synthesized in porous materials with ultraviolet and x-ray lithography. For this, the pore-filling solvent of silica hydrogels is exchanged with an aqueous solution of a group II metal ion together with a chalcogenide precursor such as 2-mercaptoethanol, thioacetamide or selenourea. The chalcogenide precursor is photodissociated in the exposed regions, yielding metal chalcogenide nanoparticles. Patterns are obtained by using masks appropriate to the type ofradiation employed. The mean size of the quantum dots is controlled by adding capping agents such as citrate or thioglycerol to the precursor solution, and the quantum yield of the composites can be increased to up to about 30% by photoactivation. Our technique is water-based, uses readily available reagents, and highly luminescent patterned composites are obtained in a few simple processing steps. Polydispersity, however, is high (around 50%), preventing large-scale usage of the technique for the time being. Future developments that aim at a reduction of the polydispersity are presented.
- A. Yamilov and M. Bertino, Optics Letters 32, 283-285 (2007)
Abstract
We demonstrate that a photonic lattice with short- and long-range harmonic modulations of the refractive index facilitates formation of flat photonic bands and leads to slow propagation of light. The system can be considered a coupled-resonator optical waveguide (CROW): photonic bands with abnormally small dispersion are created due to the interaction of long-lived states in the cavity regions via weak coupling across tunneling barriers. Unlike previous CROW implementations, the proposed structures can be fabricated with interference photolithography (holography), sidestepping the issue of resonator-to-resonator fluctuation of the system parameters. The proposed holography-based approach enables fabrication of arrays with a large number of coupled optical resonators, which is necessary for practical applications.
- A. Yamilov, and H. Cao, Physical Review E 74, 056609 (2006)
Abstract
Introduction of optical gain in a disordered system results in enhanced fluctuations of the dimensionless conductance, similar to the effect of Anderson localization in a passive medium. Using numerical simulations we demonstrate that, despite such qualitative similarity, the whole distribution of the conductance of amplifying random media is drastically different from that of a passive system with the same value.
- X. Wu, W. Fang, A. Yamilov, A. Chabanov, A. A. Asatryan, L. C. Botten, and H. Cao, Physical Review A 74, 053812 (2006)
Abstract
We present detailed experimental and numerical studies of random lasing in weakly scattering systems. The interference of scattered light, which is weak in the passive systems, is greatly enhanced in the presence of high gain, providing coherent and resonant feedback for lasing. The lasing modes are confined in the vicinity of the pumped volume due to absorption of emitted light outside it. In the ballistic regime where the size of the gain volume is less than the scattering mean free path, lasing oscillation occurs along the direction in which the gain volume is most extended, producing directional laser output. The feedback for lasing originates mainly from backscattering of particles near the boundaries of the pumped region. It results in nearly constant frequency spacing of lasing modes, which scales inversely with the maximum dimension of the gain volume.
- (invited) A. Yamilov, R. Weaver, and O. Lobkis, Photonic Spectra pp. 90-94 (August 2006)
Abstract
In his seminal paper, Albert Einstein introduced the concept of stimulated emission of electromagnetic radiation that led to the invention of masers and lasers. Ever since, there has been a propensity to regard stimulated and spontaneous emission as quantum-mechanical effects. However, these concepts have clear classical (nonquantum) analogues that we demonstrate in experiments with ultrasound.
- R. Weaver, O. Lobkis, and A. Yamilov, physics/0509215; Why do we call it a UASER? An ultrasonic analog for a laser, R. Weaver, O. Lobkis, and A. Yamilov, J. Acoust. Soc. Am. 119, 3413 (2006)
Abstract
We report measurements on ultrasonic systems analogous to random lasers. One system entails unstable ultrasonic feedback between distinct transducers, another involves a piezoelectric device that emits spontaneously and by stimulation. Both systems are found to exhibit behaviors similar to those of lasers. Over a wide range of parameters we observe narrow single emission lines, sensitivity to linear cavity properties, complex multi-mode emissions, and line narrowing.
- M. Scharrer, A. Yamilov, X. Wu, H. Cao, and R. P. H. Chang, Applied Physics Letters 88, 201103 (2006)
Abstract
UV lasing in three-dimensional ZnO photonic crystals is demonstrated at room temperature. The photonic crystals are inverse opals with high refractive index contrast that simultaneously confine light and provide optical gain. Highly directional lasing with tunable wavelength is obtained by optical pumping. Comparison of the experimental results to the calculated band structure shows that lasing occurs in high-order bands with abnormally low group velocity. This demonstrates that the high-order band structure of three-dimensional photonic crystals can be used to effectively confine light and enhance emission. Our findings may also impact other applications of photonic crystal devices.
- X. Wu, A. Yamilov, X. Liu, S. Li, V. P. Dravid, R. P. H. Chang, and H. Cao , Proc. SPIE 6122, 612205 (2006)
Abstract
We fabricated two dimensional photonic crystal structures in zinc oxide films with focused ion beam etching. Lasing is realized in the near ultraviolet frequency at room temperature under optical pumping. From the measurement of lasing frequency and spatial profile of the lasing modes, as well as the photonic band structure calculation, we conclude that lasing occurs in either localized or extended defect modes near the dielectric edge of photonic band gap. These defect modes originate from the structure disorder unintentionally introduced during the fabrication process. Fine tuning of lasing wavelength across 20nm range has been realized by varying the lattice constant of PhCS structure. A qualitative explanation for these PhCS lasers with self optimization of laser cavity quality factor has been proposed.
- X. Wu, W. Fang, A. Yamilov, A. Chabanov, and H. Cao, Proc. SPIE 6101, 61010M (2006)
Abstract
We demonstrate lasing in a cavity formed by two Mie scatterers in a dye colloidal solution. Like a Fabry-Perot cavity, the feedback mechanism for lasing is based on back scattering from each particle. Strong light amplification in between the scatterer pair not only compensate its large diffraction loss, but also help to choose the particular pair out of many scatterers in the suspension to form the laser cavity. Such cavity selection is facilitated by a careful designed cone shaped excitation geometry. Detailed experimental studies on the threshold behavior, spectral characteristic of lasing emission, and output directionality are presented. A simple theoretical model provides qualitative explanation for this lasing phenomenon.
- A. Yamilov, X. Wu, X. Liu, R. P. H. Chang, and H. Cao, Physical Review Letters 96, 083905 (2006) For more information click here.
Abstract
We studied numerically and experimentally the effects of structural disorder on the performance of ultraviolet photonic crystal slab lasers. Optical gain selectively amplifies the high-quality modes of the passive system. For these modes, the in-plane and out-of-plane leakage rates may be automatically balanced in the presence of disorder. The spontaneous optimization of in-plane and out-of-plane confinement of light in a photonic crystal slab may lead to a reduction of the lasing threshold.
- A. Yamilov, X. Wu, and H. Cao, Journal of Applied Physics 98, 103102 (2005)
Abstract
We recently reported on the realization of ultraviolet photonic crystal laser based on zinc oxide. Here we present the details of structural design and its optimization. We develop a computational supercell technique that allows a straightforward calculation of the photonic band structure of ZnO photonic crystal slab on sapphire substrate. We find that despite the small index contrast between the substrate and the photonic layer, the low-order eigenmodes have predominantly transverse-electric or transverse-magnetic polarization. Because emission from ZnO thin film shows a strong TE preference, we are able to limit our consideration to TE bands, spectrum of which can possess a complete photonic band gap with an appropriate choice of structure parameters. We demonstrate that the geometry of the system may be optimized so that a sizable band gap is achieved.
- A. Yamilov, X. Wu, H. Cao, and A. L. Burin, Optics Letters 30, 2430 (2005)
Abstract
We present a numerical study of lasing modes in diffusive random media with local pumping. The reabsorption of emitted light suppresses the feedback from the unpumped part of the sample and effectively reduces the system size. The lasing modes are dramatically different from the quasi modes of the passive system (without gain or absorption). Even if all the quasi modes of a passive diffusive system are extended across the entire sample, the lasing modes are still confined in the pumped volume with an exponential tail outside it. The reduction of effective system volume by absorption broadens the distribution of decay rates of quasi modes and facilitates the occurrence of discrete lasing peaks.
- H. Cao, A. Yamilov, A. L. Burin, and X. Wu, Proc. SPIE Int. Soc. Opt. Eng. 5924, 59240A (2005)
Abstract
We investigate the lasing modes in diffusive random media with local pumping. The reabsorption of emitter light suppresses the feedback from the unpumped part of the sample and effectively reduces the system size. The lasing modes are dramatically different from the quasimodes of the passive system (without gain or absorption). Even if all the quasimodes of a passive diffusive system are extended across the entire sample, the lasing modes are still confined in the pumped volume with an exponential tail outside it. The reduction of effective system volume by absoption broadens the distribution of decay rates of quasimodes and facilitates the occurrence of discrete lasing peaks.
- W. Fang, A. Yamilov, and H. Cao, Physical Review A 72, 023815 (2005)
Abstract
We present a numerical study of the high-quality modes in two-dimensional dielectric stadium microcavities. Although the classical ray mechanics is fully chaotic in a stadium billiard, all of the high-quality modes show a strong scar around unstable periodic orbits. When the deformation ratio of the length of the straight segments over the diameter of the half circles is small, the high-quality modes correspond to whispering gallery- type trajectories and their quality factors decrease monotonically with increasing deformation. At large deformation, each high-quality mode is associated with multiple unstable periodic orbits. Its quality factor changes nonmonotonically with the deformation, and there exists an optimal deformation for each mode at which its quality factor reaches a local maximum. This unusual behavior is attributed to the interference of waves propagating along different constituent orbits that could minimize light leakage out of the cavity.
- K. Seal, A. K. Sarychev, H. Noh, D.A. Genov, A. Yamilov, V. M. Shalaev, Z. C. Ying, H. Cao, Physical Review Letters 94, 226101 (2005)
Abstract
Spatial intensity correlation functions are obtained from near-field scanning optical microscope measurements of semicontinuous metal-dielectric films. The concentration of metal particles on a dielectric surface is varied over a wide range to control the scattering strength. At low and high metal coverages where scattering is weak, the intensity correlation functions exhibit oscillations in the direction of incident light due to excitation of propagating surface waves. In the intermediate regime of metal concentration, the oscillatory behavior is replaced by a monotonic decay as a result of strong scattering and anomalous absorption. Significant differences in the near-field intensity correlations between metallic and dielectric random systems are demonstrated.
- M. Scharrer, X. Wu, A. Yamilov, H. Cao, R.P.H. Chang, Applied Physics Letters 86, 151113 (2005)
Abstract
We have fabricated three-dimensional optically active ZnO photonic crystals by infiltrating polystyrene opal templates using a low-temperature atomic layer deposition process. The polystyrene is removed by firing the samples at elevated temperatures, and reactive ion etching is used to remove the top layer of ZnO and expose the s111d photonic crystal surface. The resulting structures have high filling fractions, possess photonic band gaps in the near-UV to visible spectrum, and exhibit efficient photoluminescence.
- A. Yamilov, A. Burin, H. Cao, S. H. Chang, and A. Taflove, Physical Review B 71, 092201 (2005)
Abstract
We study local and nonlocal correlations of light transmitted through active random media. The conventional approach results in divergence of ensemble-averaged correlation functions due to the existence of lasing realizations.We introduce a conditional average for correlation functions by omitting the divergent realizations. Our numerical simulation reveals that amplification does not affect local spatial correlation. The nonlocal intensity correlations are strongly magnified due to selective enhancement of the contributions from long propagation paths. We also show that by increasing gain, the average mode linewidth can be made comparable to the average mode spacing. This implies that light transport through a diffusive random system with gain may exhibit some similarities with that through a localized passive system.
- X. Liu, A. Yamilov, X. Wu, J. Zheng, H. Cao, R.P.H. Chang, Chemistry of Materials 16, 5414 (2004)
Abstract
We show results on how the morphology of a ZnO layer can have a big impact on the random lasing threshold of the material. Plasma-enhanced chemical vapor deposition method is used to grow ZnO layers on sapphire substrates. The morphologies and structures of ZnO are observed to undergo transition when growth temperature decreases from 750 to 100C: the deposited ZnO changes from crystalline films to nanocrystalline films with columnar shaped grains, then to well-aligned ZnO nanorods, and finally to randomly oriented irregular shaped grains. ZnO nucleation and surface diffusion rates, coalescence between crystal grains, and preferential growth along c-axis play important roles in this transition from continuous films to nanorods. Random lasing properties of our ZnO films and nanorods are studied. The scattering ability of ZnO is critical to control the lasing properties. The lowest lasing thresholds are observed for ZnO films grown between 500 and 600C when the films have columnar-shaped grains and not at 750 C when the ZnO layer has a continuous crystalline film. Calculations based on quasi-2D random lasing are consistent with the experimental results of lasing threshold measurements.
- X. Wu, A. Yamilov, X. Liu, S. Li, V. P. Dravid, R. P. H. Chang and H. Cao, Applied Physics Letters 85, 3657 (2004)
Abstract
We fabricated two-dimensional photonic crystal structures in zinc oxide films with focused-ion-beam etching. Lasing is realized in the near-ultraviolet frequency at room temperature under optical pumping. From the measurement of lasing frequency and spatial profile of the lasing modes, as well as the photonic band structure calculation, we conclude that lasing occurs in the strongly localized defect modes near the edges of photonic band gap. These defect modes originate from the structure disorder unintentionally introduced during the fabrication process.
- H. Cao, A. Yamilov, B. Liu, J.-Y. Xu, Y. Ling, E. Seelig, R. P. H. Chang, Proc. SPIE Int. Soc. Opt. Eng. 5508, 216 (2004)
Abstract
We review our recent work on lasing in active random media. Light scattering, which had been regarded detrimental to lasing action for a long time, actually provided coherent feedback for lasing. We also trapped laser light in micrometer-sized random media. The trapping was caused by disorder-induced scattering and interference. This nontraditional way of light confinement has important application to microlasers. The threshold of random laser can be reduced by incorporating some degree of order into an active random medium. Our calculation result shows that by optimizing the degree of order one can dramatically reduce the threshold of random laser to the values comparable to those of photonic bandgap defect lasers.
- A. Yamilov, and H. Cao, Physical Review E 70, 037603 (2004)
Abstract
We numerically study the statistical distribution of intensity of light transmitted through quasi-one-dimensional random media by varying the dimensionless conductance g and the amount of absorption or gain. A markedly non-Rayleigh distribution is found to be well fitted by the analytical formula of Nieuwenhuizen et al. [Phys. Rev. Lett. 74, 2674 (1995)] with a single parameter g. We show that in the passive random system g' is uniquely related to g, while in amplifying or absorbing random media g' also depends on the gain or absorption coefficient.
- S. H. Chang, A. Taflove, A. Yamilov, A. Burin, H. Cao, Opt. Lett. 29, 917 (2004)
Abstract
We applied a finite-difference time domain algorithm to the study of field and intensity correlations in random media. Close to the onset of Anderson localization, we observe deviations of the correlation functions, in both shape and magnitude, from those predicted by the diffusion theory. Physical implications of the observed phenomena are discussed.
- X. H. Wu, A. Yamilov, H. Noh, H. Cao, E. W. Seelig, and R. P. H. Chang, Journal of the Optical Society of America B 21, 159 (2004)
Abstract
We report experimental and theoretical studies of the random lasing threshold and its fluctuation in an ensemble of highly packed spherical dielectric scatterers. The ratio of the sphere diameter to the lasing wavelength was varied in a wide range, which covered the transition from the weak Rayleigh scattering regime to the strong Mie scattering regime. Experimentally, when the diameters of monodispersed ZnO spherical particles changed from less than 100 to more than 600 nm we observed a drastic decrease of the lasing threshold at small-particle size followed by a plateau at large particle size. We attribute this effect to the particle-size dependence of transport mean free path lt, which was deduced from coherent backscattering measurements. Theoretical calculation of lt reproduced experimental behavior. Using the finite-difference time domain method, we obtained the lasing threshold and its standard deviation as functions of particle size in two-dimensional systems. The results of our numerical simulations are in qualitative agreement with the experimental data.
- A. Yamilov and H. Cao, Physical Review A 69, 031803(R) (2004)
Abstract
We studied the modes of the highest-quality factor Qm in disordered photonic crystals. By varying the strength of disorder, we identified five different scaling regimes of the ensemble averaged <Qm> with the system size. For sufficiently large systems, <Qm> reaches the maximum at some finite degree of disorder, where its value is comparable to the quality factor of an intentionally introduced single defect at the center of a photonic band gap. Near this optimal degree of disorder, we predict a super-exponential increase of <Qm> with the system size, due to migration of the frequencies of the highest-quality modes toward the photonic band-gap center. Our result may lead to the design and fabrication of ultralow-threshold random laser.
- L. I. Deych, M. V. Erementchouk, A. A. Lisyansky, A. Yamilov, H. Cao, Physical Review B 68, 174203 (2003)
Abstract
We numerically study the distribution function of the conductance (transmission) in the one-dimensional tight-binding Anderson and periodic-on-average superlattice models in the region of fluctuation states where single parameter scaling is not valid. We show that the scaling properties of the distribution function depend upon the relation between the systems length L and the length ls determined by the integral density of states. For long enough systems, L>>ls , the distribution can still be described within a new scaling approach based upon the ratio of the localization length lloc and ls . In an intermediate interval of the systems length L, lloc<<L<<ls , the variance of the Lyapunov exponent does not follow the predictions of the central limit theorem and this scaling becomes invalid.
- G.S. Solomon, Z. Xie, W. Fang, J.Y. Xu, A. Yamilov, H. Cao, Y. Ma, S.T. Ho, Physica Status Solidi B 238(2) 309-312 (2003)
Abstract
Measuring the enhancement of spontaneous emission decay rates of quantum dot emission coupled to microcavity modes is typically hampered by variable coupling of the quantum dot emission. This is particularly evident in the microdisk cavity since the whispering gallery modes are localized near the disk edge, while quantum dot emitters are typically uniformily distributed throughout the disk. The distribution of spontaneous emission decay rates under these circumstances can be determined using a distribution function for the various spontaneous decay rates, and demonstrate that large decay rate enhancement are present. To remove the spatial coupling variation, quantum dots are selectively placed near the microdisk edge. Initial photoluminescence measurements indicate that recombination processes in these quantum dots are not dominated by surface recombination.
- H. Cao, A. Yamilov, J. Xu, E. Seelig, R. P. Chang, Proceedings of SPIE 4995, 134 (2003)
Abstract
We review our recent work on lasing in active random media. Light scattering, which had been regarded detrimental to lasing action for a long time, actually provided coherent feedback for lasing. We also trapped laser light in micrometer-sized random media. The trapping was caused by disorder-induced scattering and interference. This nontraditional way of light confinement has important application to microlasers. The threshold of randomm laser can be reduced by incorporating some degree of order into an active random medium. Our calculation result shows that by optimizing the degree of order one can dramatically reduce the threshold of random laser to the values comparable to those of photonic bandgap defect lasers.
- B. Liu, A. Yamilov, and H. Cao, Applied Physics Letters 83, 1092 (2003)
Abstract
We studied the effect of Kerr nonlinearity on lasing in defect modes of weakly disordered photonic crystals. Our time-independent calculation based on self-consistent nonlinear transfer matrix method shows that Kerr nonlinearity modifies both frequencies and quality factors of defect modes. We also used a time-dependent algorithm to investigate the dynamic nonlinear effect. Under continuous pumping, the spatial sizes and intensities of defect lasing modes are changed by Kerr nonlinearity. Such changes are sensitive to the nonlinear response time.
- B. Liu, A. Yamilov, Y. Ling, J. Y. Xu and H. Cao, Physical Review Letters 91, 063903 (2003)
Abstract
We have studied both experimentally and numerically the dynamic effect of nonlinearity on lasing in disordered medium. The third-order nonlinearity not only changes the frequency and size of lasing modes, but also modifies the laser emission intensity and laser pulse width. When the nonlinear response time is longer than the lifetime of the lasing mode, the nonlinearity changes the laser output through modifying the size of the lasing mode.When the nonlinear response is faster than the buildup of the lasing mode, positive nonlinearity always extracts more laser emission from the random medium due to the enhancement of single particle scattering.
- A. Yamilov and H. Cao, Physical Review B 68, 085111 (2003)
Abstract
We introduce a numerical recipe for calculating the density of the resonant states of the clusters of dielectric spheres. Using truncated multipole expansions generalized multi-sphere Mie solution! we obtain the scattering matrix of the problem. By introducing an infinitesimal absorption in the spheres we express the dwell time of the electromagnetic wave in terms of the elements of the scattering matrix. Using the parameters in recent light localization experiments, we demonstrate that the density of the resonant states, related to the dwell time, shows the formation of the photonic band structure in small clusters of dielectric spheres as the small as five particles. Density of resonant states of a cluster of 32 spheres exhibits a well defined structure similar to the density of electromagnetic states of the infinite photonic crystal. Our results suggest that, due to the formation of small ordered clusters, a significant modification of the density of electromagnetic states can occur in a random collection of mono-disperse spheres.
- E.W.Seelig, B. Tang, A. Yamilov, H. Cao, R.P.H. Chang , Materials Chemistry and Physics 80(1), 257-263 (2003)
Abstract
We present a novel method for the controlled synthesis of monodisperse ZnO colloidal spheres. These spheres are self-assembled into fcc periodic arrays. Optical measurements, including reflection-mode optical microscopy and transmission and single-domain reflection spectroscopy, reveal that the periodic arrays exhibit a photonic band gap in the (111) direction of the fcc lattice, and calculations are presented to estimate the effective value of the refractive index of the colloidal spheres. Finally, photoluminescence (PL) measurements show that the ZnO lasing thresholds are lower in periodic structures than in random arrays of identical spheres.
- W. Fang, J. Y. Xu, A. Yamilov, H. Cao, Y. Ma, S. T. Ho, G. S. Solomon, Optics Letters 27, 948 (2002)
Abstract
We have studied the enhancement of spontaneous emission rates for InAs quantum dots embedded in GaAs micro-disks in a time-resolved photoluminescence experiment. Inhomogeneous broadening of the quantum dot energy levels and random spatial distribution of the quantum dots in a micro-disk lead to a broad distribution of the spontaneous emission rates. Using a nonnegative least-norm algorithm, we extract the distribution of spontaneous emission rates from the temporal decay of emission intensity. The maximum spontaneous emission enhancement factor exceeds 10.
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, Nanotechnology 13, 114 (2002)
Abstract
Optical spectra of Bragg multiple quantum wells with defects are studied analytically and numerically. It is shown that in systems with relatively strong exciton–photon coupling several different types of spectrum can be observed. The effects due to inhomogeneous exciton broadening are studied using numerical simulations.
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, "Nanostructures: Physics and Technology", p. 273 Ioffe Physico-Technical Institute Press, Russia 2001
Abstract
Defect polariton states in Bragg multiple-quantum-well structures are studied along with defect induced changes in transmission and reflection spectra. Analytical results for eigen frequenciesof the local states and for respective transmission coefficients are obtained. It is shown that the local polaritons result in resonance tunneling of light through the stop band of MQW structure, but unlike other types of local states, the transmission resonance frequencies are always shifted with respect to eigen frequencies of the local modes. Exciton homogeneous broadening is taken into account phenomenologically and recommendations regarding the experimental observation of the predicted effects are given.
- M. Foygel, A. Yamilov, L.I. Deych, and A.A. Lisyansky, Physical Review B, 64, 115203 (2001)
Abstract
We study the local states within the polariton band gap that arise due to deep defect centers with strong electron-phonon coupling. Electron transitions involving deep levels may result in alteration of local elastic constants. In this case, substantial reversible transformations of the impurity polariton density of states occur, which include the appearance/disappearance of the polariton impurity band, and its shift and/or the modification of its shape. These changes can be induced by thermo- and photoexcitation of the localized electron states or by trapping of injected charge carriers. We develop a simple model, which is applied to the OP center in GaP. Further possible experimental realizations of the effect are discussed.
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, Physical Review B 64, 024201 (2001)
Abstract
Numerical study of the scaling of transmission fluctuations in the one-dimensional localization problem in the presence of absorption is carried out. Violations of single-parameter scaling for lossy systems are found and explained on the basis of a new criterion for different types of scaling behavior derived by Deych et al. Phys. Rev. Lett. 84, 2678 (2000).
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, Physical Review B 64, 075321 (2001)
Abstract
We study analytically defect polariton states in Bragg multiple quantum well structures and defect-induced changes in transmission and reflection spectra. Defect layers can differ from the host layers in three ways: exciton-light coupling strength, exciton resonance frequency, and inter-well spacing. We show that a single defect leads to two local polariton modes in the photonic band gap. These modes cause peculiarities in reflection and transmission spectra. Each type of defect can be reproduced experimentally, and we show that each of these plays a distinct role in the optical properties of the system. For some defects, we predict a narrow transmission window in the forbidden gap at the frequency set by parameters of the defect. We obtain analytical expressions for corresponding local frequencies as well as for reflection and transmission coefficients. We show that the presence of the defects leads to resonant tunneling of the electromagnetic waves via local polariton modes accompanied by resonant enhancement of the field inside the sample, even when a realistic absorption is taken into account. On the basis of the results obtained, we make recommendations regarding the experimental observation of the effects studied in readily available samples.
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, Optics Letters 25, 1705 (2000)
Abstract
We study analytically the optical properties of several types of defect in Bragg multiple-quantum-well structures. We show that a single defect leads to two local polariton modes in the photonic bandgap. These modes lead to peculiarities in reflection and transmission spectra. Detailed recommendations for experimental observation of the effects studied here are given.
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, Physical Review B 62, 6301 (2000)
Abstract
The concept of local polaritons is used to describe the optical properties of mixed crystals in the frequency region of their restrahlen band. It is shown that this concept allows for a physically transparent explanation of the presence of weak features in the spectra of so-called one-mode crystals and for one-two mode behavior. The previous models were able to explain these features only with the use of many fitting parameters. We show that under certain conditions new impurity-induced polariton modes may arise within the restrahlen of the host crystals, and study their dispersion laws and density of states. Particularly, we find that the group velocity of these excitations is proportional to the concentration of the impurities and can be thousands of times smaller than the speed of light in vacuum.
- A. Yamilov, L.I. Deych, and A.A. Lisyansky, Journal of the Optical Society of America B 17, 1498 (2000)
Abstract
A detailed analytical study of an impurity-induced polariton band arising inside a spectral gap between lower and upper polariton branches is presented. Using the micro-canonical method, we calculate the density of states and the localization length of the impurity polaritons. Analytical results are compared with numerical simulations, and excellent agreement is found.
- A. Yamilov, L.I. Deych, and A.A. Lisyansky, Ann. Phys. 8, 293 (1999)
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, Physical Review B 59, 11339 (1999)
Abstract
We consider tunneling of electromagnetic waves through a polariton band gap of a one-dimensional chain of atoms. We analytically show that a defect embedded in the structure gives rise to the resonance transmission at the frequency of a local polariton state associated with the defect. Numerical Monte Carlo simulations are used to examine properties of the electromagnetic band arising inside the polariton gap due to finite concentration of defects.
- L.I. Deych, A. Yamilov, and A.A. Lisyansky, Europhysics Letters 46, 524 (1999)
Abstract
We consider tunneling of electromagnetic waves through a polariton band gap of a 1-D chain of atoms. We analytically demonstrate that a defect embedded in the structure gives rise to the resonance transmission at the frequency of a local polariton state associated with the defect. Back to top <a
Invited talks
- Physics Seminar, University of Missouri Columbia (2025)Coherent control of wave propagation in opaque materials
- Workshop on Collective Scattering of Light, FDN, Brazil (2024)Anderson Transition and Critical Exponent for Light in a Three-Dimensional Random Medium
- University of Texas in San Antonio, TX (2024)Anderson localization of electromagnetic waves in three dimensions
- Physics of Quantum Electronics (PQE), Snowbird, UT (2024)Anderson localization of electromagnetic waves in three dimensions
- Physics Colloquium, Missouri S&T (2023)Anderson localization of electromagnetic waves: or how to solve a problem in under 40 years
- Physics of Quantum Electronics (PQE), Snowbird, UT (2023)Coherent enhancement of optical remission in diffusive media
- Physics Colloquium, Missouri S&T (2022)When random walk is not so random : coherent control of wave propagation in opaque materials
- Laboratoire de Physique et Modelisation des MilieuxCondenses, CNRS, Grenoble, France (2022) Coherent control of wave propagation inside scattering media
- 12th International Conference on ElasticElectrical, Transport, and Optical Properties of Inhomogeneous Media (ETOPIM12), Besancon, France (2022) Depth-targeted energy delivery deep inside scattering media
- Queens College, City University of New YorkFlushing, NY (2022) Controlling wave propagation inside scattering media
- FlexCompute Inc., Belmont, MA (2021)Anderson localization of light
- CLEO 2020, San Jose, CA, (2020)Statistics of Individual Eigenchannels of Diffusive Random Medium
- SPIE Metamaterials, Metadevices, and Metasystems2018, San Diego, CA (2018) Strategies for enhanced injection of light into scattering medium
- MRS Spring Meeting, Phoenix, AZ (2018)Wave propagation via eigenchannels of scattering medium
- École Supérieure de Physique et de ChimieIndustrielles (ESPCI), Paris, France (2017) Custom-made eigenchannels, or how to choose the eigenchannel that’s right for you
- The Institute for Computational and Experimental Researchin Mathematics (ICERM), Brown University, RI (2017) Determinism of wave transport and eigenchannels of multiple scattering media
- Illinois State University, Normal, IL (2017)Random or comlex? Looking through walls and around the corner
- Physics of Quantum Electronics (PQE), Snowbird, UT(2017) Eigenchannels in scattering media: from manipulation to inverse design
- 7th Internation Conference on MetamaterialsPhotonic Crystals and Plasmonics, META 2016, Spain (2016), Eigenchannels in scattering media
- Missouri S&T Chemistry (2016)Coherent control of wave transport in scattering media: Looking through walls and around the corner
- Workshop on “Waves and imaging in random media,”Institut Henri Poincare, Paris, France (2015) Control of mesoscopic transport by modifying transmission channels in scattering media
- École Polytechnique de Montréal, QC, Canada (2015)New approach to control light transport in random media
- 9th International Conference on Nonlinear EvolutionEquations and Wave Phenomena, Athens, GA (2015) Control of light transport via non-local wave interference effects in random media
- Wesleyan University, Middletown, CT (2015)Control of light transport in random media
- 9th International Workshop on DisorderedSystems, San Antonio, TX (2014) Interplay between localization and absorption in disordered waveguides
- Summer school "Waves and disorder," Cargese, France(2014) Wave localization in open random media as position-dependent diffusion: Analytical, numerical and experiment results
- Yale University (2013)Position-dependent diffusion in absorbing random media
- University of Texas - Dallas (2012)Regimes of wave transport in absorbing random media
- Workshop on “Recent developments in wave propagationand imaging in complex media,” Institut Henri Poincare, Paris (2012) Regimes of wave transport in absorbing random media
- Old Dominion University, Norfolk Virginia(2012) Mesoscopic Optics
- University of Missouri Columbia (2011)Teaching an online physics course: from psycology to technology
- Board of Currators Meeting, Rolla (2011)Wave Propagation in Random Media
- Washington University in Saint Louis (2011)Misoscopic Optics
- Missouri State University, Springfield, MO (2011)Mesoscopic Optics: Carrot laser anyone?
- University of North Carolina at Charlotte (2010)Mesoscopic Physics of Photons: Particle Versus Wave Transport Through Random Media
- UMKC, March (2010)Particle Versus Wave Transport Through Random Media
- Missouri S&T Chemistry colloquium (2009)Mesoscopic physics of photons
- University of Missouri – St. Louis (2009)Mesoscopic physics of photons: from Anderson localization to random lasing
- International Diffuse Reflectance SpectroscopyConference, Chambersburg, PA (2008) Simulations and statistical analysis of electromagnetic wave propagation in random amplifying media
- El Centro de Investigación Científica y deEducación Superior de Ensenada (CICESE) at Ensenada, Mexico (2008) Mesoscopic Phenomena in Disordered Waveguides
Conference presentations
- Bioinnovation and Medical Engineering Symposium, Rolla, MO, June 2025Coherent-wave control for deep sensing in biomedical applications
- GDR Complexe Annual Meeting, Paris, France, November 2024Towards Anderson localization of light in three dimensions
- CLEO/Europe 2023, Munich, Germany, June 2023Delivering Broadband Light Deep into Diffusive Media
- 2023 International Applied Computational Electromagnetics Society Symposium, ACES, Monterey, CA, March 2023Simulation of Coherent Remission in Planar Disordered Medium
- SummerSchool "Waves in complex media", Cargese, France, September 2022 Suppressing background for wave focusing in diffusive media L. Shaughnessy, C.W. Hsu, N. Bender, A. Goetschy, H. Yilmaz, A. Yamilov and H. Cao
- SummerSchool "Waves in complex media", Cargese, France, September 2022 Depth-targeted energy delivery deep inside scattering media A. Yamilov, N. Bender, A. Goetschy, H. Yılmaz, C.W. Hsu and H. Cao
- CLEO/QELS 2021, San Jose, CA, May 2021Fluctuations and correlations of transmission eigenchannels within diffusive media
- ComplexNanophotonic Science Camp 2019, London, UK, August 2019 Transmission eigenchannels in a wide multiple-scattering slab H. Yilmaz, C. W. Hsu, A. Yamilov, and H.Cao
- CLEO/QELS2019, San Jose, CA, May 2019 Transverse localization of transmission eigenchannels in the diffusive regime H. Yilmaz, C. W. Hsu, A. Yamilov, and H.Cao
- CLEO/QELS2019, San Jose, CA, May 2019 Memory effect of transmission eigenchannels in random media H. Yilmaz, C. W. Hsu, A. Yamilov, and H. Cao
- CLEO/QELS2018, San Jose, CA, May 2018 Coherent injection of light into lossy micro-porous scattering medium A. Yamilov, R. Sarma, V. V. Yakovlev, and H. Cao
- Photonics West2018, San Francisco, CA, January 2018 Transverse localization of transmission eigenchannels H. Yilmaz, C. W. Hsu, A. Yamilov, H. Cao
- Metamaterials2017, Marseille, France, August 2017 Partial Coherence Uncloaks Diffusive Optical Invisibility Cloaks A. Niemeyer, F. Mayer, A. Naber, M. Koirala, A. Yamilov, M. Wegener
- CLEO/QELS2017, San Jose, CA, May 2017 Inverse Design of Eigenchannels in Scattering Media M. Koirala, R. Sarma, H. Cao and A. Yamilov
- Summerschool "Spatio-Temporal Control of Waves," Cargese, France (2017) Transmission eigenchannels of disordered media in open geometry H. Yilmaz, C. Wei Hsu, A. Yamilov and H. Cao
- CLEO/QELS2016, San Jose, CA, June 2016 Detection of diffusive cloak via second-order statistics M. Koirala and A. Yamilov
- Frontiersin Optics 2016, Rochester, NY, Oct. 2016 Control of Optical Intensity Distribution inside a Disordered Waveguide H. Cao, R. Sarma, Y. Bromberg, A. Yamilov, S. Petrenko
- Frontiersin Optics 2015, San Jose CA, Oct. 2015 Control of Transmission Eigenchannels by Modifying the Geometry of Turbid Media R. Sarma, A. Yamilov, H. Cao
- CLEO/QELS2015, San Jose, CA, May 2015 Critical States Embedded in the Continuum A. Yamilov, M. Koirala, A. Basiri, Y. Bromberg, H. Cao, T. Kottos
- 6thInternation Conference on Metamaterials, Photonic Crystals and Plasmonics (META15), New York, NY, Aug. 2015 Light Localization in the Presence of Non-Hermitian Defects A. Basiri, M. Koirala, A. Yamilov, Y. Bromberg, H. Cao, T. Kottos
- Frontiersin Optics 2014, Tucson, AZ, Oct. 2014 (i) Probing Long Range Intensity Correlations inside Disordered Photonic Waveguides R. Sarma, A. Yamilov, P. Neupane, B. Shapiro, H. Cao (ii) Controlling Diffusion of Light inside a Disordered Photonic Waveguide R. Sarma, T. Golubev, A. Yamilov, H. Cao (iii) Wave localization as position-dependent diffusion: analytical results P. Neupane, A. Yamilov (iv) Critical States Embedded in the Continuum M. Koirala, A. Yamilov, A. Basiri, Y. Bromberg, H. Cao, T. Kottos
- APSMarch meeting, Denver, CO, March 2014 Transverse Light Localization in waveguide arrays with random absorption or amplification A. Basiri, Y. Bromberg, A. Yamilov, H. Cao, and T. Kottos,
- CLEO/EUROPEMunich, May 2013 Position-Dependent Diffusion of Light in Disordered Waveguides A. Yamilov, R. Sarma, B. Redding, B. Payne, H. Noh, and H. Cao
- Teachingand Learning Technology Conference, Rolla, MO, March 2013 Teaching Nanotechnology with Technology A. Yamilov
- MidwestSection Conference of the ASEE, Rolla, November 2012 (Proceedings) Teaching an Undergraduate Nanotechnology Course Online A. Yamilov
- Frontiersin Optics 2012, Rochester, NY, Oct. 2012 (i) Artificially disordered birefringent optical fibers S. Herath, N. P. Puente, E.I. Chaikina, and A. Yamilov (ii) 2D Thue-Morse array of optical cavities: tight-binding model B. Payne, L. Sisken, H. Noh, H. Cao, and A. Yamilov (iii) Universality of wave transport in absorbing random media A. Yamilov and B. Payne
- APSMarch meeting, Boston MA, March 2012 Position-dependent diffusion coefficient as localization criterion in non-conservative random media B. Payne and A. Yamilov
- Physicsof Quantum Electronics (PQE) 2012, Snowbird, UT, January 2012 Characterization of wave transport in non-conservative random media (invited) A. Yamilov and B. Payne
- Frontiersin Optics 2011, San Jose, CA, Oct. 2011 (i) Position-Dependent Diffusion Coefficient as Localization Criterion in non-Conservative Random Media B. Payne and A. Yamilov
- Recentdevelopments in wave physics of complex media, Cargese, France, May 2011 Classification of regimes of wave transport in non-conservative random media B. Payne and A. Yamilov
- Frontiersin Optics 2010, Rochester NY, Oct. 2010 (i) Frequency correlation between eigenmodes of disordered waveguides B. Payne and A. Yamilov (ii) Anderson localization as position-dependent diffusion in disordered waveguides B. Payne, A. Yamilov, and S. E. Skipetrov (iii) Fabrication and characterization of controlled disorder in the core of the optical fibers N. P. Puente, E. I. Chaikina, S. Herath, and A. Yamilov
- Physicsof Quantum Electronics (PQE) 2010, Snowbird, UT, January 2010 Survey of regimes of wave transport in random waveguides with gain or absorption (invited) A. Yamilov and B. Payne
- Frontiersin Optics 2009, San Jose, CA, Oct. 2009 (i) Classification of regimes of wave transport in non-conservative random media B. Payne and A. Yamilov (ii) Effect of evanescent modes on conductance distribution in disordered waveguides B. Payne, T. Mahler and A. Yamilov
- ElectricalTransport and Optical Properties of Inhomogeneous Media – ETOPIM 8, Greece, June 2009 Criterion for light localization in random amplifying media Ben Payne*, Johnathan Andreasen, Hui Cao and Alexey Yamilov
- Frontiersin Optics 2008, Rochester, NY, Oct. 2008 On criterion for light localization in random amplifying media Ben Payne*, Alexey Yamilov, Jonathan Andreasen, Hui Cao Relation between channel and spatial mesoscopic correlations in volume-disordered waveguides Alexey Yamilov
- TheQuantum Electronics and Laser Science Conference (QELS), San Jose CA, May 2008 Trench Waveguide in Photonic Crystal Slab Alexey G. Yamilov, Mark Herrera*
- Frontiersin Optics 2007, San Jose CA, September 2007 (i) Mesoscopic Correlations in Disordered Waveguide: Dependence on Channel Indexes Alexey Yamilov (ii) Effect of Local Pumping on 1-D Random Laser Modes Xiaohua Wu, Jonathan Andreasen, Hui Cao, Alexey Yamilov (iii) Waveguiding in Photonic Crystal Slab with Variable Thickness Mark Herrera*, Massimo Bertino, Alexey Yamilov
- ThePhotonic Metamaterials: From Random to Periodic Topical Meeting, Jackson Hole WY, June 2007 (i) Effect of Local Pumping on Random Laser Modes, Xiaohua Wu, Jonathan Andreasen, Hui Cao, Alexey Yamilov (ii) Factorization of Mesoscopic Intensity Correlations, Alexey Yamilov, Andrey Chabanov, Azriel Z. Genack, Hui Cao
- Frontiersin Optics 2006, Rochester NY, October 2006 (i) Quasi-Modes in Disordered Waveguide with Gain Alexey Yamilov (ii) UV Lasing near the First ?L-Pseudogap of ZnO Inverse Opals Michael Scharrer, Xiaohua Wu, Alexey Yamilov, Hui Cao, Robert P. H. Chang (iii) Light Propagation through Dual-Periodic 1D Photonic Crystal Alexey Yamilov, Mark Herrera*, Massimo Bertino (iv) An Ultrasonic Analogue for a Random Laser Alexey Yamilov, Richard W. Weaver, Oleg Lobkis
- Frontiersin Optics 2005, Tucson AZ, October 2005 (i) Disorder Optimizes the Performance of UV Photonic Crystal Laser Alexey G. Yamilov, Xiaohua H. Wu, Hui Cao (ii) Absorption Induced Confinement of Lasing Modes in Diffusive Random Medium Alexey G. Yamilov, Alexander L. Burin, Xiaohua H. Wu, Hui Cao (iii) Mesoscopic Optics Andrey Chabanov, Alexey Yamilov, Hui Cao, Bing Hu, Azriel Genack (iv) Near-Field Intensity Correlation in Semicontinuous Metal Films Hui Cao, Katyayani Seal, Andrey K. Sarychev, Dentcho A. Genov, Vladimir M. Shalaev, Alexey Yamilov, Heeso Noh, Charles Z. Ying (v) Effect of Amplification on Distribution of Conductance in Disordered Waveguide Alexey G. Yamilov, Hui Cao
- SPIEOptics and Photonics: Nanophotonics, Complex Mediums, San Diego, CA, July 2005 Lasing in disordered photonic crystals Hui Cao, Alexey Yamilov, Xiaohua Wu, Michael Scharrer, R.P.H. Chang
- Frontiersin Optics 2004, Rochester NY, October 10-14. (i) Mode coupling in open chaotic microcavities Alexey G. Yamilov, Wei Fang, Hui Cao (ii) Study of high quality modes in fully chaotic microcavities Hui Cao, Wei Fang, Alexey Yamilov (iii) Ultraviolet photonic crystal lasers Xiaohua Wu, Alexey Yamilov, Xiang Liu, Shuyou Li, Vinayak P. Dravid, Robert P. H. Chang, Hui Cao (iv) Intensity distribution in passive and amplifying random media near localization threshold Alexey G. Yamilov, Hui Cao
- Frontiersin Optics 2003, Tucson AZ, October 6-10. (i) Effects of gain and localization on the light correlation in random media A. Yamilov, S. H. Chang, A. Burin, H. Cao, A. Taflove (ii) Study of random lasing in closely-packed resonant scatterers X. Wu, A. Yamilov, X. Liu, S. Li, V. P. Dravid, R. P. H. Chang and H. Cao
- 2ndInternational Conference on Semiconductor Quantum Dots, Tokyo, Japan, September 30 - October 3 2002. Large Spontaneous Emission Enhancement in InAs Quantum Dots Coupled to Microdisk Whispering Gallery Modes G.S. Solomon, Z. Xie, W. Fang, J.Y. Xu, A. Yamilov, H. Cao, Y. Ma, S.T. Ho.
- PIERS2003 in Hawaii, Progress in Electromagnetics Research Symposium, 13-16 October 2003, Honolulu, Hawaii, USA Lasing in Closely Packed Resonant Nanoscatterers Hui Cao, Xiaohua Wu, Alexey Yamilov, Eric Seelig, Robert Chang
- MRS2002 Spring Meeting: Photonic Crystals--From Materials to Devices, San Francisco, CA (April, 2002) 3D photonic crystals from monodisperse ZnO colloidal spheres Eric W. Seelig, Betty Tang, R.P.H. Chang, Alexey Yamilov, Hui Cao
- 2002Annual Meeting of the Optical Society of America, Orlando, FL (October, 2002)
- 9thInternational Symposium. Nanostructures: Physics and Technology, St. Petersburg, Russia (June, 2001)
- MarchMeeting of the American Physical Society, Seattle, WA (March, 2001) (i) Photoinduced transformation of polariton impurity band in semiconductors M. Foygel, A. Yamilov, L.I. Deych, and A.A. Lisyansky (ii) Polariton local states in periodic Bragg MQW structures L.I. Deych, A. Yamilov, and A.A. Lisyansky (iii) Concept of local polaritons A. Yamilov, L.I. Deych, and A.A. Lisyansky (iv) Single parameter scaling in localized absorbing systems L.I. Deych, A. Yamilov, and A.A. Lisyansky
- WavePropagation in New York City and other Random Media, Yeshiva University, New York (July, 2000)
- Localization1999 - Disorder and Interaction in Transport Phenomena, International Conference, Hamburg, Germany (July, 1999)
- MarchMeeting of the American Physical Society, Atlanta, GA (March, 1999) Resonant tunneling of electromagnetic waves through a polariton gap, L.I. Deych, A. Yamilov, and A.A. Lisyansky
- The79th Statistical Mechanics Meeting, New Brunswick, NJ (May, 1998)
Current collaborators
- Hui Cao, Department of Applied Physics, Yale University — light transport and manipulation in complex nanophotonic media
- Sergey Skipetrov, LPMMC, CNRS Grenoble — wave localization
- Flexcompute Inc. — large-scale wave simulations
- Matthieu Davy, Université de Rennes — localization of microwaves
- Lorenzo Pattelli, European Laboratory for Non-Linear Spectroscopy — light localization
- Alexander Petrov, Technische Universität Hamburg — light localization
- Arthur Goetschy, Institut Langevin, ESPCI Paris — coherent control of wave propagation in turbid media
- Hasan Yilmaz, Bilkent University — coherent control of wave propagation in turbid media
- Mikhail Berezin, Washington University in St. Louis — non-invasive optical imaging in biological systems
- Vlad Yakovlev, Texas A&M — non-invasive optical imaging in biological systems
Research funding
Awarded grants
- 2020 – 2024
- National Science Foundation, "Collaborative Research: Wave transport via eigenchannels of complex media", DMR-1905442 (PI)
- 2012 – 2016
- National Science Foundation, "Collaborative Research: Anomalous Transport and Wavefront Shaping in Complex Photonic Media", DMR-1205223 (PI)
- 2007 – 2011
- National Science Foundation, "Collaborative Research: Mesoscopic Transport and Localization in Active Random Media", DMR-0704981 (PI)
- 2009 – 2010
- University of Missouri Research Board, "Electromagnetic wave transport through disordered amplifying optical fibers" (PI)
Computational time grants
- 2009 – 2011
- TeraGrid, "Non-diffusive transport and localization in the random amplifying medium", DMR-090132, DMR-100030; 1,100,000 SU