My research interests and expertise can be broadly described as wave
propagation in complex media. It spans the areas of condensed matter
physics, optics and photonics. I conduct analytical and numerical modeling
with a view toward experimental corroboration.
Wave propagation in complex
(random, aperiodic, partially or fully ordered) media
Coherent control of wave transport
and imaging in turbid media
Wave diffusion in confined
geometries, localization phenomena
Lasing in complex photonic media
Compressive sensing and machine
learning algorithms and optimization
MS in Physics/Engineering (summa
cum laude) Study of multicomponent systems in
the framework of the renormalization group equation
1995 - 1997 Donetsk State University, Ukraine
BS in Physics Application of Kadanoff-Baym
kinetic equations to calculation of electro-conductivity in
disordered systems
1992 - 1995 Donetsk State University, Ukraine
2020 - 2023 National
Science Foundation, "Collaborative
Research: Wave transport via eigenchannels of complex media"
DMR-1905442
2012 - 2016 National
Science Foundation, "Collaborative
Research: Anomalous Transport and Wavefront Shaping in Complex Photonic
Media" DMR-1205223
2007 - 2011 National
Science Foundation, "Collaborative
Research: Mesoscopic Transport and Localization in Active Random
Media" DMR-0704981
2009 - 2010 University
of
Missouri Research Board, "Electromagnetic
wave transport through disordered amplifying optical fibers"
Computational Time Grants
2009 - 2011 Tera-Grid,
"Non-diffusive transport and localization
in the random amplifying medium" DMR-090132, DMR-100030; 1,100,000
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Other
professional
activities and memberships
Referee
for APS, OSA, SPIE, Nature journals; NSF,
Eropean funding agencies; CLEO topical program commettee, NSF panels Organizer
of Condensed Matter Seminar at Northwestern University Member
CLEO/QELS
– Fundamental Sciences: Metamaterials and Complex Media Subcommittee
2015-2018 Subcommittee
chair CLEO/QELS – Fundamental Sciences: Metamaterials and
Complex Media Subcommittee 2016-2-18 Presider
at Frontiers in Optics, CLEO/QELS Organizer
of Physics DepartmentColloquium
at Missouri S&T 2008-2011 http://physics.mst.edu/currentcourses/seminars.html
1. Hui Cao, Department of
Applied Physics, Yale University
Light Transport and Manipulation in Complex Nano-Photonic Media
2. Lei Tian,
Deparment of Electrical and Computer Engineering, Boston University
Computational Imaging
3. Ulugbek Kamilov,
Deparment of Electrical and Systems Engineering, Washington University in
St. Louis
Computational Imaging
4. Vladislav
Yakovlev, Texax A&M
Diffusion is structured random media
5. Martin
Wegener, Karlsruhe Institute of Technology
Cloaking in diffusive media
6. Tsampikos Kottos,
Physics Deparment, Wesleyan University
Localization in systems with complex potential
7. Sergey
Skipetrov, CNRS
Self-consistent Theory of Localization
83.
Coherent enhancement of
optical remission in diffusive media,
N. Bender, A. Goetschy, C. W. Hsu, H. Yilmaz, P. Jara Palacios, A.
Yamilov, H. Cao, (submitted) 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.
82.Roadmap
on Wavefront Shaping and deep imaging in complex media,
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, accepted (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 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 on this field, that 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.
81. Depth-Targeted
Energy Deposition Deep Inside Scattering Media,
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.
80. Fluctuations
and correlations of transmission eigenchannels in diffusive media,
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.
79. Angular
memory effect of transmission eigenchannels,
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.
78. Inverse
design of long-range intensity correlation in scattering 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.
77. Transverse
localization
of transmission eigenchannels,
H. Y?lmaz, 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.
76. Coherent
injection
of light into absorbing scattering medium with a microscopic pore,
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.
75. Enhanced
optical
coupling and Raman scattering via microscopic interface engineering,
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, 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.
74. Inverse
design
of perfectly transmitting eigenchannels in scattering media,
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.
73. Enhanced
coupling
of light into a turbid medium through microscopic interface engineering,
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.
72. Uncloaking
diffusive-light
invisibility cloaks by speckle analysis,
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.
71. Enhancing
light
transmission through a random medium with inhomogeneous scattering and
loss,
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.
70. Control
of
energy density inside disordered medium by coupling to open or closed
channels,
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.
69. Detection
of diffusive cloak via second-order statistics,
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.
68. Shape-dependence
of transmission, reflection and absorption eigenvalue densities in
disordered waveguides with dissipation,
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.
67. Control
of mesoscopic transport by modifying transmission channels in opaque 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.
66. Using
geometry to manipulate long-range correlation of light inside disordered
media,
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.
65. Applicability
of
the position-dependent diffusion approach to localized transport through
disordered waveguides,
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.
64. Critical
states
embedded in the continuum,
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.
63. Light
localization
induced by a random imaginary refractive index,
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.
62. Controlling
diffusion
inside a disordered nanophotonic waveguide using geometry,
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.
61. Probing
Long-range
intensity correlations inside disordered photonic nanostructures,
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.
60. Position-dependent
diffusion
of light in disordered waveguides, (supplementary information
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.
59. Interplay
between
localization and absorption in disordered waveguides,
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.
58. Effect
of evanescent channels on position-dependent diffusion in disordered
waveguides,
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.
57. Artificially
disordered
birefringent optical fibers,
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.
56. Self-optimization
of
optical confinement and lasing action in disordered photonic crystals,
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.
55. Fabrication,
characterization
and theoretical analysis of controlled disorder in the core of the
optical fibers,
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.
54. Investigations
of
mode coupling in optical fibers with controlled volume disorder,
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.
53. Classification
of
regimes of wave transport in quasi-one-dimensional non-conservative random
media,
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.
52. Relation
between transmission and energy stored in random media with gain,
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.
51. Anderson
localization
as position-dependent diffusion in disordered waveguides,
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.
50. Dual-Periodic
Photonic
Crystal Structures,
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.
49. Criterion
for light localization in random amplifying media,
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.
48. Five-fold
reduction
of lasing threshold near the first ?L-pseudogap of ZnO inverse opals,
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.
47. Relation
between channel and spatial mesoscopic correlations in volume-disordered
waveguides,
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.
46. Slow-light
effect in dual-periodic photonic lattice,
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.
45. Entrainment
and stimulated emission of auto-oscillators in an acoustic cavity,
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.
44. Effect
of
local pumping on random laser modes,
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.
43. Quantum
dots
by ultraviolet and X-ray lithography,
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.
42. Disorder-immune
coupled
resonator optical waveguide,
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.
41. Effect
of
amplification
on
conductance distribution of a disordered waveguide,
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.
40. Lasing
with
coherent
feedback in weakly scattering media,
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.
39. UASER:
Ultrasound
Amplification by Stimulated Emission of Radiation, (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.
38. Ultrasonic
analog
for random laser,
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.
37. Ultraviolet
lasing
in high-order bands of three-dimensional ZnO photonic crystals,
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.
36. ZnO
photonic
crystal lasers,
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.
35. Laser
resonators
formed by two nanoparticles,
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.
34. Self-optimization
of
optical confinement in ultra-violet photonic crystal slab laser,
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.
33. Photonic
band
structure
of ZnO photonic crystal slab laser,
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.
32. Absorption-induced
confinement
of lasing modes in diffusive random medium,
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.
31. Interplay
between
amplification and absorption in diffusive random lasers,
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.
30. Analysis
of
high-quality
modes in open chaotic microcavities,
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.
29. Near-field
intensity
correlations in semicontinuous metal-dielectric films,
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.
28. Fabrication
of inverse opal ZnO photonic crystals by atomic layer deposition,
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.
27. Field
and intensity correlations in amplifying random media,
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.
26. Effect
of ZnO Nanostructures on 2-dimensional random lasing properties,
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.
25. Ultraviolet
photonic crystal laser,
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.
24. Dynamic
nonlinear
effect on lasing in random media,
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.
23. Effects
of localization and amplification on intensity distribution of light
transmitted through random media
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.
22. Numerical
study of light correlations in a random medium close to the Anderson
localization threshold
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.
21. Random
lasing in closely packed resonant scatterers,
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.
20. Highest-quality
modes in disordered photonic crystals,
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.
19. Statistics
of transmission in one-dimensional disordered systems: universal
characteristics of states in the fluctuation tails,
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.
18. 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,
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.
17. Lasing
in
disordered
media,
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.
16. Effect
of Kerr nonlinearity on defect lasing modes in weakly disordered
photonic crystals,
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.
15. Dynamic
nonlinear effect on lasing in random medium,
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.
14. Manifestation
of photonic band structure in small clusters of spherical particles,
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.
13. Self-assembled
3D photonic crystals from ZnO colloidal 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.
12. Large
enhancement of spontaneous emission rates of InAs quantum dots in GaAs
microdisks,
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.
11. Optical
spectra and inhomogeneous broadening in CdTe/CdZnTe MQW structures with
defects,
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.
10. Polariton
local
states in periodic Bragg multiple quantum well structures,
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.
9. Tunable
local polariton states,
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.
8. Scaling
in one-dimensional localized absorbing systems,
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).
7. Local
polariton modes and resonant tunneling of electromagnetic waves through
periodic Bragg multiple quantum well structures,
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.
6. Polariton
local states in periodic Bragg multiple quantum well structures,
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.
5. Concept
of local polaritons and optical properties of mixed polar crystals,
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.
4. Impurity-induced
polaritons in a one-dimensional chain,
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.
3. Polariton
impurity
band,
A. Yamilov, L.I. Deych, and A.A. Lisyansky, Ann. Phys. 8,
293 (1999)
2. Effects
of resonant tunneling in electromagnetic wave propagation through a
polariton gap,
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.
1. Defect-induced
resonant tunneling of electromagnetic waves through a polariton gap,
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.
46. Complex
Nanophotonic 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
45. CLEO/QELS
2019, San Jose, CA, May 2019 Transverse
localization of transmission eigenchannels in the diffusive regime H. Yilmaz, C. W. Hsu, A. Yamilov, and H.Cao
44. CLEO/QELS
2019, San Jose, CA, May 2019 Memory effect
of transmission eigenchannels in random media H. Yilmaz, C. W. Hsu, A. Yamilov, and H. Cao
43. CLEO/QELS
2018, 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
42. Photonics
West 2018, San Francisco, CA, January 2018 Transverse
localization of transmission eigenchannels
H. Yilmaz, C. W. Hsu, A. Yamilov, H. Cao
41. Metamaterials
2017, Marseille, France, August 2017 Partial
Coherence Uncloaks Diffusive Optical Invisibility Cloaks
A. Niemeyer, F. Mayer, A. Naber, M. Koirala, A. Yamilov, M. Wegener
40. CLEO/QELS
2017, San Jose, CA, May 2017 Inverse Design
of Eigenchannels in Scattering Media
M. Koirala, R. Sarma, H. Cao and A. Yamilov
38. Summer school
"Spatio-Temporal Control of Waves," Cargese, Corsica, France (2017)
Transmission
eigenchannels of disordered media in open geometry
H. Yilmaz, C. Wei Hsu, A. Yamilov and H. Cao
38. CLEO/QELS
2016, San Jose, CA, June 2016 Detection of
diffusive cloak via second-order statistics
M. Koirala and A. Yamilov
37. Frontiers in
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
36. Frontiers in
Optics 2015, San Jose CA, Oct. 2015 Control of
Transmission Eigenchannels by Modifying the Geometry of Turbid Media
R. Sarma, A. Yamilov, H. Cao
35. CLEO/QELS
2015, San Jose, CA, May 2015 Critical
States Embedded in the Continuum
A. Yamilov, M. Koirala, A. Basiri, Y. Bromberg, H. Cao, T. Kottos
34. 6th
Internation 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
33. Frontiers in
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
32. APS March
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,
31. CLEO/EUROPE,
Munich, May 2013 Position-Dependent
Diffusion
of Light in Disordered Waveguides
A. Yamilov, R. Sarma, B. Redding, B. Payne, H. Noh, and H. Cao
30. Teaching and
Learning Technology Conference, Rolla, MO, March 2013 Teaching
Nanotechnology with Technology
A. Yamilov
29. Midwest
Section Conference of the ASEE, Rolla, November 2012 (Proceedings) Teaching an
Undergraduate Nanotechnology Course Online
A. Yamilov
28. Frontiers in
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
27. APS March
meeting, Boston MA, March 2012 Position-dependent
diffusion
coefficient as localization criterion in non-conservative random media
B. Payne and A. Yamilov
26. Physics of
Quantum Electronics (PQE) 2012, Snowbird, UT, January 2012 Characterization
of
wave transport in non-conservative random media (invited)
A. Yamilov and B. Payne
25. Frontiers in
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
24. Recent
developments in wave physics of complex media, Cargese, Corsica,
France, May 2011 Classification
of regimes of wave transport in non-conservative random media
B. Payne and A. Yamilov
23. Frontiers in
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
22. Physics of
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
21. Frontiers in
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
20. Electrical
Transport 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
19. Frontiers in
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
18. The Quantum
Electronics and Laser Science Conference (QELS), San Jose CA, May
2008 Trench
Waveguide in Photonic Crystal Slab
Alexey G. Yamilov, Mark Herrera*
17. Frontiers in
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
16. The Photonic
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
15. Frontiers in
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
14. Frontiers in
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
13. SPIE, Optics
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
12. Frontiers in
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
11. Frontiers in
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
10. 2nd
International 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.
9. PIERS
2003 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
8. MRS 2002
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
7. 2002 Annual
Meeting of the Optical Society of America, Orlando, FL (October,
2002)
6. 9th
International Symposium. Nanostructures: Physics and Technology,
St. Petersburg, Russia (June, 2001)
5. March Meeting
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
4. Wave
Propagation in New York City and other Random Media, Yeshiva
University, New York (July, 2000)
3. Localization
1999 - Disorder and Interaction in Transport Phenomena,
International Conference, Hamburg, Germany (July, 1999)
2. March Meeting
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
1. The 79th
Statistical Mechanics Meeting, New Brunswick, NJ (May, 1998)
29. CLEO 2020, San Jose, CA, (2020) Statistics of
Individual Eigenchannels of Diffusive Random Medium
28. SPIE Metamaterials, Metadevices, and Metasystems 2018, San
Diego, CA (2018) Strategies for
enhanced injection of light into scattering medium
27. MRS Spring Meeting, Phoenix, AZ (2018) Wave
propagation via eigenchannels of scattering medium
26. École Supérieure de Physique et de Chimie Industrielles
(ESPCI), Paris, France (2017) Custom-made
eigenchannels, or how to choose the eigenchannel that’s right for you
25. The Institute for Computational and Experimental Research in
Mathematics (ICERM), Brown University, RI (2017) Determinism of
wave transport and eigenchannels of multiple scattering media
24. Illinois State University, Normal, IL (2017) Random or
comlex? Looking through walls and around the corner
23. Physics of Quantum Electronics (PQE), Snowbird, UT (2017) Eigenchannels
in scattering media: from manipulation to inverse design
22. 7th Internation Conference on Metamaterials, Photonic
Crystals and Plasmonics, META 2016, Spain (2016), Eigenchannels
in scattering media
21. Missouri S&T Chemistry (2016) Coherent
control of wave transport in scattering media: Looking through walls and
around the corner
20. Workshop on “Waves and imaging in random media,” Institut
Henri Poincare, Paris (2015) Control of
mesoscopic transport by modifying transmission channels in scattering
media
19. École Polytechnique de Montréal, QC, Canada (2015) New approach
to control light transport in random media
18. 9th International Conference on Nonlinear Evolution
Equations and Wave Phenomena, Athens, GA (2015) Control of
light transport via non-local wave interference effects in random media
17. Wesleyan University, Middletown, CT (2015) Control of
light transport in random media
16. 9th International Workshop on Disordered Systems, San
Antonio, TX (2014) Interplay
between localization and absorption in disordered waveguides
15. Summer school "Waves and disorder," Cargese, Corsica, France
(2014) Wave
localization in open random media as position-dependent diffusion:
Analytical, numerical and experiment results
14. Yale University (2013) Position-dependent
diffusion
in absorbing random media
13. University of Texas - Dallas (2012) Regimes of
wave transport in absorbing random media
12. Workshop on “Recent developments in wave propagation and
imaging in complex media,” Institut Henri Poincare, Paris (2012) Regimes of
wave transport in absorbing random media 11. Old Dominion University, Norfolk Virginia (2012)
Mesoscopic Optics 10. University of Missouri Columbia (2011) Teaching an
online physics course: from psycology to technology
9. Board of Currators Meeting, Rolla (2011) Wave
Propagation in Random Media 8. Washington University in Saint Louis (2011) Misoscopic
Optics
7. Missouri State University, Springfield, MO (2011)
Mesoscopic Optics: Carrot laser anyone?
6. University of North Carolina at Charlotte (2010) Mesoscopic
Physics of Photons: Particle Versus Wave Transport Through Random Media 5. UMKC, March (2010) Particle
Versus Wave Transport Through Random Media
4. Missouri S&T Chemistry (2009) Mesoscopic
physics of photons
3. University of Missouri – St. Louis (2009) Mesoscopic
physics of photons: from Anderson localization to random lasing
2. International Diffuse Reflectance Spectroscopy Conference,
Chambersburg, PA (2008) Simulations
and statistical analysis of electromagnetic wave propagation in random
amplifying media 1. El Centro de Investigación Científica y de Educación
Superior de Ensenada (CICESE) at Ensenada, Mexico (2008) Mesoscopic
Phenomena in Disordered Waveguides
