January 22-24, 2017Tata Institute of Fundamental Research, Mumbai
The first International Workshop on Complex Photonics is aimed at bringing together international leading experts in studies of light transport in disordered media, covering subfields
such as Anderson localization of light, random lasers, quantum and nonlinear optics of disordered systems and so on. We envisage active interactions of these experts with early career researchers in India, including senior graduate students, postdocs and young faculty.
Accordingly, each talk is expected to maintain a common flow, a generous pedagogical introduction followed by technical narrative of latest research results.
The photonics community in India is growing rapidly. The meeting is expected to introduce the young participants to the exciting facets of complex photonics,
and encourage them to identify potential common grounds in their own research. We hope that this meeting seeds the formation of a broader Mesoscopic Optics community in India.
All Lectures will be held in Lecture Hall,AG-66,Ground Floor,TIFR.
Please click on the time slots to view the details and abstract of the talks.
Location: Lecture hall, AG-66,TIFR
Prof. Claudio Conti
University of Rome
"Random Lasers: from granulars to biomimetic paper"
We will review our experimental activity on random lasers. This will include shaken granulars, paper and
biomimetic systems. We will also report on the control of the interaction of modes in random lasers and the link
with the science of complex systems. Some results on theoretical models will also be discussed.
Prof. Allard Mosk
Light in Complex Systems, Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands.
"Shaped waves and speckle correlations."
Random scattering of light, which takes place in paper, paint and biological tissue is an obstacle to
imaging and focusing of light and thus hampers many applications. At the same time scattering is a
phenomenon of basic physical interest as it allows the study of fascinating interference effects such as
open transport channels [1,2], which enable lossless transport of waves through strongly scattering materials.
Propagation of laser light in scattering media can be controlled by shaping the incident wavefront
using spatial light modulators. Wavefront shaping methods in scattering media have given rise to a
new wave of fundamental studies of light propagation as well as new modalities of imaging and
focusing with scattered light. Recently we demonstrated that speckle correlations enable non-invasive
fluorescence imaging through strongly scattering layers . Scattering “lenses” made of high-index
materials allow wide-field speckle-illumination microscopy with a resolution approaching 100 nm .
In waveguides scattering can be exceptionally strong. We have very recently demonstrated dynamic
control of resonant scattering using light, which allows interactive control of scattering , with the
possibility to create a new class of adaptive nanophotonic circuits.
 A. P. Mosk, A. Lagendijk, G. Lerosey, and M. Fink, Controlling waves in space and time for
imaging and focusing in complex media, Nat. Photon., 6, 283 (2012).
 I.M. Vellekoop and A.P. Mosk, Universal optimal transmission of light through disordered
materials, Phys. Rev. Lett. 101, 120601 (2008).
 J. Bertolotti, E. G. van Putten, C. Blum, A. Lagendijk, W. L. Vos, and A. P. Mosk, Non-invasive
imaging through opaque scattering layers, Nature, 491, 232 (2012).
 H. Yılmaz, E. G. van Putten, J. Bertolotti, A. Lagendijk, W. L. Vos, and A. P. Mosk, Exploiting
speckle correlations to improve the resolution of wide-field fluorescence microscopy, Optica 2,424 (2015).
 S. Sokolov, J. Lian, E. Yüce, S. Combrié, G. Lehoucq, A. De Rossi, and A. P. Mosk, Local
thermal resonance control of GaInP photonic crystal membrane cavities using ambient gas
cooling, Appl. Phys. Lett. 106, 171113 (2015).
Prof. Hema Ramachandran
Light and Matter Physics Group, Raman Research Institute,Bangalore.
"Imaging through fog and other strongly scattering media"
When light travels through homogenous media, there is a direct correspondence between
points of detection and the points on the source, enabling the formation of images. This one-to- one
correspondence, however, is almost entirely lost in the presence of dielectric inhomogenities, that cause
multiple random scattering of light. Because of this, light travels diffusively, rather than ballistically, in
strongly scattering media, rendering imaging difficult. This problem is widely encountered in a variety of
fields – medical imaging, underwater exploration, navigation under poor visibility, etc. Techniques for
imaging through scattering media have been developed over the decades, especially in the context of
medical imaging. Most studies employ either laboratory colloidal suspensions, or tissue samples.
However, there is, in literature, no systematic study of imaging through real fog, in the field. It is not
clear whether the finding in the laboratory experiments are valid for real atmospheric fog.
This talk will begin with an overview of common imaging techniques, and then will progress to
describe recent work on imaging through atmospheric fog over distances exceeding a kilometer.
Thereafter, some recent results on real-time imaging through strongly scattering media will be
Prof. Anderson Gomes
Physics Department, Universidade Federal of Pernambuco, Cidade Universitária,
Recife, 50670-901, PE, Brazil
"Complex Photonics in Random Fiber Lasers."
In recent years, complexity has been recognized as a ubiquitous feature of nature.
From cosmic to cell evolution to the internet of things, many systems have evolved to
a high degree of complexity. This is not different in photonics, and researchers have
been playing and learning with different photon-based systems considering their
complex behavior. Among such systems, random lasers (RL) stand out as being an
open, disordered system based on scattering particles in the presence of a gain
medium, which makes them a fascinating case for studying its complex behavior. Over
the last two to three decades, great advances in the understanding of RL operation,
particularly the feedback mechanism which exploits scattering rather than two
conventional mirrors, opened possibilities for multidisciplinary studies using them as
photonic platforms. It is now understood that although RL do not have cavities (in the
conventional way), they have modes and that their tunability, directionality and
polarization properties can be managed. RL operation from nature based to man-made
devices has been demonstrated. Wavelength operation has been demonstrated from
the UV to the FIR, while optical and electrical pumping has also been employed. These
aspects are reviewed in [1-8]. Until 2007, random lasers were demonstrated in 2D or
3D systems, when de Matos et al  demonstrated the first random fiber laser (RFL)
operation. Since then, a great diversity of different 1D or quasi-1D fiber lasers have
been operated, with applications in telecommunications and sensors, as recently
In this talk, I shall review the recent development in RFL, and place emphasis to RFL
based on random fiber Bragg gratings (FBG) as the scattering element. Using such a
specially designed FBG Erbium based RFL (Er-RFL), we shall describe our results on
Lévy-like behavior of the Er-RFL , observed in 2D and 3D RL, as reported in  and
refs. therein, as well as the observation of replica symmetry breaking , which is a
signature of spin glass behavior of random laser first demonstrated in 2015 , as
recently reviewed in . We will show that, as in 3D systems , the observation of
Lévy behavior and RSB are obtained from the same set of measurements, and this is
theoretically supported since both evolve from the Langevin equations on the
amplitudes of the normal modes. We will also report on preliminary results on the
observation of the distribution of maximum intensities in the Er-RFL that may be
explained through a hierarchical stochastic model that is akin to Kolmogorov's theory
 H. Cao, Wave Random Media 13, R1—R39 (2003).
 H. Cao, J. Phys. A 38, 10497—10535 (2005).
 M.A. Noginov, Solid-State Random Lasers, Springer, New York, 2005.
 D.S. Wiersma, Nat. Phys. 4, 359—367 (2008).
 D.S. Wiersma, Nat. Photonics 7, 188—196 (2013)
 F. Luan, B. B. Gu, A. S. L. Gomes, K. T. Yong, S. C. Wen, P. N. Prasad, Nano Today 10,
 S. F. Yu, J. Phys. D: 48, 483001-28 (2015).
 L. Sznitko, J. Mysliwiec, A. Miniewicz, Journal of Polymer Science, Part B: Polymer
Physics 53, 951–974 (2015).
 C. J. S. de Matos, L. de S. Menezes, A. M. Brito-Silva, M. A. Martinez Gámez, A. S. L.
Gomes, and C. B. de Araújo, Phys. Rev. Lett. 99, 153903 (2007).
 S. K. Turitsyn, S. A. Babin, D. V. Churkin, I. D. Vatni, M. Nikuli, E. V. Podivilov,
Physics Reports 542, 133–193 (2014).
 D. V. Churkin, S. Sugavanam, I. D. Vatnik, Z. Wang, E. V. Podivilov, S. A. Babin, Y.
Rao, S. K. Turitsyn, Adv. Opt. Photonics 7, 516-569 (2015).
 B. C. Lima, A. S. L. Gomes, P. I. R. Pincheira, A. L. Moura, M. Gagné, E. P. Raposo, C.
B. de Araújo, R. Kashyap, J. Opt. Soc. Am. B, Accepted (2016).
 R. Uppu, S. Mujumdar, Phys. Rev. Lett. 114, 183903 (2015).
 A. S. L. Gomes, B. C. Lima, P. I. R. Pincheira, A. L. Moura, M. Gagné, E. P. Raposo, C.
B. de Araújo, and R. Kashyap, Phys. Rev. A 94, 011801(R) (2016).
 N. Ghofraniha, I. Viola, F. Di Maria, G. Barbarella, G. Gigli, L. Leuzzi, C. Conti, Nat.
Commun. 6, 6058 (2015).
 F. Antenucci, A. Crisanti, M. Ibáñez-Berganza, A. Marruzzo, L. Leuzzi, Phil. Mag. 96,
 A. S. L. Gomes, E. P. Raposo, A. L. Moura, S. I. Fewo, P. I. R. Pincheira, V. Jerez, L. J.
Q. Maia, C. B. de Araújo, Sci. Rep. 6, 27987 (2016).
Prof. R P Singh
Physical Research Laboratory, Ahmedabad
"Vortex scattering through random scattering media"
Optical vortices also known as whirlpools of light and optical tornados can be
generated in the laboratory in a controlled manner using different techniques. Instead
of plane or spherical wavefront, they carry helical wavefront that gives orbital angular
momentum to the light bearing these structures. This peculiar property of the beam
along with the dark core at the centre finds variety of applications in communication,
astronomy, and optical manipulation.
We generate optical vortices of different orders and scatter them through random
scattering media. It appears that light has lost its phase structure; however, the
scattered light passing through a lens shows the same vorticity when probed at the
Fourier plane. The vorticity is measured using a nonseparable state of polarization and
orbital angular momentum of light as it cannot be confirmed by the standard
interferometric techniques. The observed vorticity is found to be independent of the
amount of scattered light collected. The results may have far reaching applications in
free space optical communication.
Dr. Somnath Ghosh
"Exceptional singularities in unconventional micro-cavities and waveguides."
Corroborating the analogy between non-Hermitian quantum system and counterpart optical
geometries with suitable amount of simultaneous inhomogeneous gain and loss, I plan to
discuss an innovative unconventional scheme for asymmetric mode conversion in a coupled
optical system under certain condition in the strong coupling regime (beyond
the PT symmetry limit) exploiting singularities (in eigen values and eigen vectors) associated
with avoided crossings (in the regime where adiabatic evolution fails) as an efficient tool.
Novel propagation dynamics of light wave through this special optical structure is evident,
which is being explored in the context of on-chip photonics applications including optical
isolation. Proposal of a special hidden singular line, connecting these EPs, in
parameter plane will also be discussed. Considering, various encircling situations,
incorporating smooth as well as fluctuating variations of the system parameters, the
optical performance in terms of stability of cascaded flip-of- state phenomenon
assisted by successive encirclement of either single or multiple EPs following the
hidden singular line in the context of optical mode converters is investigated.
Moreover, for a specific pair of coupled resonances we explore that the excess noise
generation among the interacting non-orthogonal states can be suppressed close to
the ideal value 1 with simultaneous order of magnitude enhancement in Q-factor of
the longer lived state.
Posters and Discussions
Venue: Homi Bhabha Auditorium foyer
Departure to residence
Prof. Sandip Trivedi
Venue: AG-66 Lecture Hall
Prof. Remi Carminati
Institut Langevin, ESPCI ParisTech, CNRS, Paris, France
"A few surprises in multiple scattering of light"
Light scattering and transport in disordered media has been extensively studied. On the fundamental side, the
possibility to study coherent scattering (speckles) in optics has been an essential tool in mesoscopic physics. On
the applied side, methods and techniques have been developed for sensing and imaging in complex media.
New trends have emerged recently with the possibility to control light propagation using disordered materials.
In this talk we will review recent results in the theory of light transport (diffusion) and scattering (speckles) that
predict unexpected behaviors of interest for the control of light matter-interaction.
We will discuss an invariance property of the average path length in a wave diffusion process , and the first
measurement demonstrating this invariance .
In the study of speckle patterns, we will show that a spatial correlation between the reflected and transmitted
intensities persists even in the multiple scattering regime . This makes possible to quantify the level of
information on a transmitted speckle that can be deduced from a measurement of the reflected part only.
We will finally address the influence of correlations in the disorder on the scattering strength. In the case of
hyperuniform materials (a specific class of correlated materials), we will show that disordered materials that
are both dense and transparent can be designed .
I am indebted to O. Leseur, N. Fayard, A. Goetschy and R. Pierrat with whom most of this work was done.
 R. Pierrat, P. Ambichl, S. Gigan, A. Haber, R. Carminati and S. Rotter, PNAS 111, 17765 (2014)
 R. Savo, R. Pierrat, U. Najar, R. Carminati, S. Rotter and S. Gigan, submitted for publication (2016)
 N. Fayard, A. Cazé, R. Pierrat and R. Carminati, Phys. Rev. A 92, 033827 (2015)
 O. Leseur, R. Pierrat and R. Carminati, Optica 3, 763 (2016)
Prof. Ajay Nahata
University of Utah, Salt Lake City
“The effect of disorder in THz plasmonic structures.”
Dr. Shivakiran Bhaktha
Department of Physics, Indian Institute of Technology Kharagpur, India
"Modes of an Optofluidic Random Laser"
Abstract: Experimental results on the spatial and spectral properties of the modes of 1-D and 2-D
optofluidic random lasers in the weakly scattering regime are discussed. We spatially map the
lasing modes of a weakly scattering optofluidic random laser by a pump-probe technique. The
lasing modes are observed to be concentrated at the boundaries of the gain region as predicted by
OCIS codes: 140.0140 Lasers and laser optics; 290.4210 Multiple scattering.
Fig. 1(a) Photograph of the random laser device, (b) shows the spatial intensity distribution map of the random
lasing mode at 560.40 nm.
In conventional lasers, the optical cavity that confines the photons also determines essential characteristics
of the lasing modes such as wavelength, emission pattern, and directivity. In random lasers, which do not have
mirrors or a well-defined cavity, light is confined within the gain medium by means of multiple scattering. The
sharp peaks in the emission spectra of semiconductor powders, first observed in 1999 , has therefore led to an
intense debate about the nature of the lasing modes in random lasers [2,3].
Here, we present the experimental studies aimed at clarifying the nature of the lasing modes in disordered scattering
systems with gain [4,5]. Low dimensional (1-D or 2-D) random active media are of particular interest in this context
where the possibility to image the lasing modes provides with an experimental probe of the theoretical predictions.
Beyond the fundamental questions addressed, the proposed random lasing structure in Fig. 1(a) leads to interesting
and unexpected innovative devices. Fig. 1(b) depicts the spatial intensity distribution map of the random lasing
mode at 560.40 nm. The characterization of these modes along with the details of the spatial mapping will be
presented in the conference.
 H. Cao, Y. G. Zhao, S. T. Ho, E.W. Seelig, Q. H.Wang, and R. P. H. Chang, “Random laser action in semiconductor powder,” Phys. Rev.
Lett. 82, 2278 (1999).
 D. S. Wiersma, “The physics and applications of random lasers,” Nat. Phys. 4, 359-367 (2008).
 H. Cao, “Lasing in random media”, Waves Random Media, 13, R1-R39 (2003).
 B. N. Shivakiran Bhaktha, N. Bachelard, X. Noblin, and P. Sebbah, “Optofluidic random laser,” Appl. Phys. Lett. 101,
 A. Sarkar, and B. N. Shivakiran Bhaktha, “Signatures of periodicity and randomness in the angular emission profile of a 2-D on-average
periodic optofluidic random laser”, Opt. Lett. 40, 4951 (2015).
Prof. Pepijn Pinkse
University of Twente, Netherlands
"Quantum-Secure Authentication and Adaptive Quantum Optics"
Modern society strongly relies on secret information for authentication. However, keeping information
secret and accessible is exceedingly difficult in modern society. We experimentally demonstrate
Quantum-Secure Authentication (QSA) that does not require keeping secret information but relies on an
optical Physical Unclonable Function (PUF) as a key . We illuminate the key using light containing
fewer photons than spatial degrees of freedom. In the key the photons are multiple-scattered by millions
of randomly organized nanoparticles. The spatial shape of the returned (“response”) photons depends
strongly on the positions of the scatterers and on the incident (“challenge”) photons. Assuming its
challenge-response behavior is known, the key can be authenticated by illuminating it with a challenge
and verifying whether the response is as expected. The challenge can contain very few photons, shaped
as a complex wavefront and therefore encoding for many bits of information, even for a single photon
. Not knowing the randomly chosen shape, an attacker cannot fully characterize the challenge.
Therefore, he cannot digitally construct the correct response even if the challenge-response behavior of
the key is publicly known. QSA is secure if the physical key is too complex to be copied with current
Fig 1. a, Quantum-Secure
Authentication setup. A spatial
light modulator (SLM1) transforms
a weak laser beam into a
“challenge” that contains more
spatial degrees of freedom than
photons. The optical multiplescattering
key converts the
challenge into a “response”.
SLM2 is programmed to convert
the expected response into a plane
wave. b, If the key is correct, the
few-photon response will be
focused onto the detector. c, If the
key is wrong, the few-photon
response will not be focused onto
the detector. Image from .
QSA is an intriguing application of “Adaptive Quantum Optics”, the combination of quantum optics and
adaptive optical methods counteracting or even exploiting disorder. In a recent work  we demonstrate
that with wavefront modulators, multiple-scattering materials can be turned into programmable linear
optical networks. In such a network we demonstrate programmable two-photon quantum interference.
 Quantum-secure authentication of a physical unclonable key, S. A. Goorden, M. Horstmann, A. P. Mosk, B.
Škorić, and P. W. H. Pinkse, Optica 1, 421-424 (2014)
 Transmitting more than 10 bit with a single photon, T. B. H. Tentrup, T. Hummel, T. A. W. Wolterink, R. Uppu,
A. P. Mosk, and P. W. H. Pinkse, ArXiv 1609.04200 (2016)
Dr. Rajesh Nair
Laboratory for Nano-scale Optics and Meta-materials (LaNOM),
Department of Physics, Indian Institute of Technology (IIT) Ropar, India
"Optical studies on colloidal photonic crystals"
Controlling and manipulating the light propagation and emission using nanophotonic structures is a contemporary
topic of research due its potential applications in photonics. Photonic crystals constitute a class of meta-materials
characterized with a periodically altered refractive index along three orthogonal directions. They exhibit photonic
stop gaps for light wherein the photon density of states vanishes for a range of frequencies in a given direction that
depends strongly on the polarization states of the incident light.
In this talk, we discuss the angle and polarization induced stop gaps branching at different high symmetric points in
the hexagonal facet of Brillouin zone of colloidal photonic crystal with face centered cubic (fcc) symmetry. Optical
reflectivity measurements are performed to identify the stop gap branching into two well separated peaks at K point
at an incident angle of 56° for TE polarized light. Contrary, TM polarized light does not exhibit the stop gap
splitting at the K point at much higher angle of incidence. The two different reflectivity peaks originated is assigned
to the (111) and (-111) crystal planes. We measure the polarization anisotropy factor to quantify the competition
between multiple Bragg diffraction and Brewster angle at the K point for TM polarization. The on-resonance
Brewster effect occur at much higher values of incident angle as compared to the off-resonance case due to the nontrivial
definition of effective refractive index in photonic crystals. The modification of spontaneous emission of
embedded quantum emitters in colloidal photonic crystals will also be discussed. We have performed spectral and
spatial emission measurements from single domains of colloidal crystals to elucidate the extend of suppression
possible in the colloidal photonic crystals.
Harshawardhan Wanare, IIT Kanpur
"Enhanced WAVELIKE aspects of the Photon Density Waves in amplifying random media."
“Wavelike” aspects associated with light provide powerful handle in terms
of its utility as a probe. We present significantly enhanced wavelike
character of the scalar diffuse-photon-density-waves (DPDW) in amplifying
random medium. Here, even in a dominantly randomizing (incoherent)
multiple scattering process involving photon diffusion “wavelike” aspects
not only persist but can also dominate. This results in exciting
possibilities including negative refraction, anti-surface-like modes at
interfaces, and waveguide resonances that can be utilized to extend the
imaging capabilities of the DPDW in tissue like random medium. The
existence of modes of the DPDW in this regime can be used to not only
obtain the size information but also the shape and orientation of an
inhomogeneity. The tenuous connections of these modes to lasing threshold
associated with random lasers will also be presented.
Posters and Discussions
Venue: Auditorium foyer
Bus Departure to residence
Prof. Hui Cao
Yale University, Connecticut
"Mesoscopic Optics of 2D Random Media"
In recent years, wavefront shaping has become a powerful tool for manipulating the transport of
light in disordered media. I will present our recent work on coherent control of light transmission
through a two-dimensional diffusive system. By shaping the incident wavefront, we selectively
couple a monochromatic laser beam to open or closed transmission channels. The light intensity
distribution inside the random medium can be changed from an exponential decay to a linear
decay and to a profile peaked near the center of the waveguide. We also investigate how spatially
uniform or non-uniform loss affects the transmission eigenchannels. For a broadband incident
light, we show that a specific wavefront can simultaneously enhance light transmission at all
frequencies, thanks to the long-range spectral correlations. Finally, we realize an on-chip
spectrometer with disordered photonic nanostructures. The wavelength-dependent speckle
patterns are used as a fingerprint to reconstruct the input spectra. A broadband enhancement of
spectral resolution is achieved via multiple scattering of light.
Dr. Mehul Malik
University of Vienna
"Twisted light communication through atmospheric turbulence"
A photon can carry an enormous amount of information in its spatial structure. The spatial modes of
light have recently attracted considerable interest as a means of enhancing both quantum and classical
communication systems. However, several lab-scale studies have shown that light carrying information
encoded in its orbital angular momentum experiences significant degradation in mode quality when
transmitted through atmospheric turbulence. I will discuss two recent proof-of-principle experiments
on the transmission of such light modes over macroscopic distances—3 km over the city of Vienna and 143
km between two islands in the Canaries. In both cases, simple messages were encoded in the spatial modes
of light to demonstrate the quality of the communication link. In addition, I will discuss the suitability
of these links for the distribution of high-dimensional spatial mode entanglement.
Dr. Anjani Kumar Tiwari
"Resolving the otherwise unresolved Fabry-Perot modes via random intensity fluctuations"
In this talk, I will discuss about the Fabry-Perot lasing modes that are excited in liquid crystal
elastomer film having a moderate intrinsic disorder. The Fabry-Perot cavity modes are analyzed particularly
in those films where the free spectral range is closer than the resolution limit of the spectrometer.
The intensity fluctuations induced by the intrinsic disorder provide a favorable condition for few lucky modes
which enhances prominently compared to all other existing modes. The probability distribution of these prominent
modes allows us to resolve them even if they are closer than the spectral resolution of the instrument.
Thus the working principle of this intrinsic disorder system can be considered as the spectral analogue of
stochastic optical reconstruction microscopy.
Each talk of 20 minutes.
Danveer Singh, IISER, Pune:
Probing Plasmonic and Organic Semiconductor Nanowires using Dual Channel Fourier Microscope.
Chithrabhanu P, PRL, Ahmdedabad:
A Stabilizaed Polarization Controlled Orbital Angular Momentum Sorter.
Amita Mohanty, NISER, Bhubaneswar:
Lifetimes, Leavel Energies and Light shifts in a single Trapped Ba+ Ion.
Dr. Riccardo Sapienza
Department of Physics, King’s College London, Strand, London WCR 2LS, United Kingdom.
"Unconventional lasing design, from photonic networks to biolasers"
Random lasing systems based on disorder and multiple scattering provide efficient and simple means to generate laser
light and a test-bed for out-of-equilibrium and non-linear physics. The complex multi-modal fabric that sustains lasing
lacks conventional cavity modes, and with that the emission directionality and spectrally purity, but offers the
advantage of a rich mode competition.
I will introduce network random laser made out of electrospinning of polymer nano-fibres and I will discuss
how unbalancing the mode competition is an effective strategy for spectral selection via static scattering
resonances, correlated disordered topologies, and more importantly dynamically via adaptive pumping.
Building on this I will show how we design and fabricate biocompatible random laser lasers that can be use as
sensitive sensors for living tissue integration, opening a path between complex photonics and medicine for future
Fundamental Optics, Terahertz and Optical Nanostructures Laboratory
Prof. Achanta Venu Gopal & Prof. S S Prabhu.
"Light-matter interaction in metamaterials"
Metamaterials with sub-wavelength featured metal-dielectric or all-dielectric elements are interesting for
light modulation as well as controlling the optical properties of materials. In this talk, we will summarize
the recent activities in our laboratory covering visible to near-infrared and THz wavelength regions. Some of
the recent results include setting up of a direct measurement of beam shift with 50nm precision in the VIS-NIR
region, near-field optical measurements of plasmonic structures, broadband plasmonic and all-dielectric
metamaterials, novel THz antennas and materials for enhancing THz emission and detection, THz spectroscopy to
study material properties among others.
Prof. Sushil Mujumdar
"Anderson localization and Levy sums in random lasers"
For a long time, investigations of light transport in disordered media retraced the trail of mesoscopic
studies in electronic systems, punctuated by observations such as light diffusion and the metal-insulator
transition for light. The addition of optical gain into the disordered medium, however, led to a series
of unexpected observations that initiated an idea of optical materials titled, rather fancifully,
In this talk, I will first explain the term random lasers, and then present a report of our own contributions
in frequency and intensity statistics thereof. The former study has revealed unknown facets of bandedge and
bandgap state lasing, and has led to the observation of Anderson localization with gain and the lifetime
statistics of Anderson modes. The latter study provided evidence of the manifestation of an exotic statistical
process called the truncated Levy flight in random lasers, which enabled us to completely describe the intensity
behavior on a single unique platform. Subsequently, we have also identified the role of extreme events in the
process, and have resorted to extremal statistics to maximize the efficiency of random lasers.
 A K Tiwari and S Mujumdar, Physical Review Letters, 111, 233903 (2013)
 R Uppu and S Mujumdar, Physical Review Letters, 114, 183903 (2015)
Posters and Discussions
Venue: Homi Bhabha Auditorium foyer
Departure to residence
Registrations, and the selection process, are over.