Group Members
Former Members
Studies of microcavities can be
dated from the beginning of XX century when the theory of Mie resonances was
developed. Understanding of scattering properties of microdroplets and
microparticles played an important role in developing radar technology after
Second World War. During last two decades this area experienced steady growth
due to applications of microspheres, cylinders, rings, and toroids in active
and passive chip-scale devices such as tunable optical filters, laser cavities
and sensors. Due to continuous progress in technology and characterization of
such cavities the quality factors of their whispering gallery modes (WGMs)
reached extremely high values ~109. Evanescent waveguide-to-cavity
and fiber-to-cavity couplers were proposed and developed. These technological
and experimental breakthroughs open new era of studies of microresonators. New
physics available in such systems include cavity quantum electrodynamics
effects, resonantly enhanced light-matter coupling phenomena including
polaritonic, plasmonic and nonlinear properties, effects of electrical,
mechanical and thermal tuning of resonators, effects of coupling between high-Q
cavities, effects of radiative pressure and electromagnetic cooling.
The research performed at
Microcavities and Mesoscopic Systems (MMS) Laboratory aims at exploring
individual ultra high-Q resonances available in a variety of semiconductor and
dielectric structures for building more complicated coupled cavity systems or
mesoscopic crystal structures with useful optoelectronic functionality. In
contrast to metamaterials conceptualized through the process of homogenization,
the optical properties of such mesoscopic systems are essentially based on the
properties of constituting cavities including their WGM resonances and
potential disorder effects. The focus is on basic physical
properties and phenomena, but some of the investigated materials may lend
themselves to photonic device applications. Most of the structures are
synthesized directly in MMS Lab using techniques of directed self-assembly of
dielectric microspheres. Some of the structures are provided by other
laboratories within the framework of national and international collaborations
such as existing collaboration with
This
project was initiated in 2003 in attempt to develop Coupled Resonator Optical
Waveguides (CROWs) [1] formed by spherical dielectric cavities with sizes in
2-30 mm range. We experimentally studied
optical transport due to coupling between WGMs in disordered chains of
polystyrene microspheres [2] and theoretically investigated WGM transport in
microcylinder CROWs [3]. Most recently we observed novel types of optical modes
and new mechanisms of optical transport in such structures. These include
experimental observation of nanojet-induced modes [4] theoretically predicted
[5] by Z. Chen et al., observation of quasi-WGMs and Fano resonances in
size-mismatched bispheres [6,7] and observation of percolation of WGMs [8] in
3D lattices of coupled spherical cavities. In this project we develop theory
and technology of such circuits of microspheres as well as new device concepts of lasers,
tunable optical delay lines, microspectrometers and sensors based on coupled
microspheres. This research is funded by ARO and
NSF.
References
[1] A. Yariv, Y.Xu,
R.K. Lee, and A. Scherer, “Coupled-resonator optical waveguide: A proposal and
analysis”, Opt. Lett. 24,
711-713 (1999).
[2] V.N. Astratov, J.P. Franchak,
and S.P. Ashili, “Optical coupling and transport phenomena in chains of
spherical dielectric microresonators with size disorder”, Appl. Phys. Lett. 85,
5508-5510 (2004).
[3] S. Deng, W. Cai, and V. N.
Astratov, “Numerical study of light propagation via whispering gallery modes in
microcylinder coupled resonator optical waveguides”, Opt. Express 12,
6468-6480 (2004).
[4] A.M. Kapitonov and V.N.
Astratov, “Observation of nanojet-inducing modes with small propagation losses
in chains of coupled spherical cavities”, Opt.
Lett. 32, 409-411 (2007).
[5] Z. Chen, A.
Taflove, and V. Backman, “Highly efficient optical coupling and transport
phenomena in chains of dielectric microspheres”, Opt. Lett. 31, 389-391
(2006).
[6] A. V. Kanaev, V. N.
Astratov, and W. Cai, “Optical coupling at a distance between detuned spherical
cavities”, Appl. Phys. Lett. 88, 111111 (2006).
[7] S.P. Ashili, V.N.
Astratov, and E.C.H. Sykes, “The effects of inter-cavity separation on optical
coupling in dielectric bispheres”, Opt.
Express 14, 9460-9466 (2006).
[8] V.N. Astratov and
S.P. Ashili, “Percolation of light in 3D lattices of spherical cavities with
coupled whispering gallery modes”, to be submitted to Appl. Phys. Lett. (2007).
In 2006 jointly with our long
standing collaborator, Low Dimensional
Structures and Devices (LDSD) group from the University of Sheffield, UK,
we observed WGMs in AlAs/GaAs pillar microcavities [1]. These modes are
interesting due to their high Q-factors
(up to 20000) and small modal volumes ~0.1 mm3 allowing efficient coupling with single
near-surface quantum dots in micropillars. These investigations of coherent
light-matter coupling through a single mode of high-Q microcavity have become
an important area of fundamental studies in quantum cavity electrodynamics with
potential applications [2] in quantum information processing and in developing
single photon sources. Some advantages of WGMs in comparison with previously
studied “photonic dot” states [3-5] in micropillars will be used in our future
work to achieve strong coupling between individual photonic and electronic
states.
References
[1] V.N. Astratov, S.
Yang, S. Lam, D. Sanvitto, A. Tahraoui, D.M. Whittaker, A.M. Fox, and M.S.
Skolnick, “Observation of whispering gallery resonances in circular and
elliptical semiconductor pillar microcavities”, to be submitted to Appl. Phys. Lett.. (2007).
[2] J.M. Gerard and B. Gayral, “InAs
quantum dots: artificial atoms for solid-state cavity-quantum electrodynamics”,
Physica E 9, 131-139 (2001).
[3] J.M. Gerard, D. Barrier, J.Y.
Marzin, R. Kuszelewicz, L. Manin, E. Costard, V. Thierry-Mieg, and T. Rivera,
“Quantum boxes as active probes for photonic microstructures: The pillar
microcavity case”, Appl. Phys. Lett. 69, 449-451 (1996).
[4] J.P. Reithmaier, M. Röhner, H.
Zull, F. Schäfer, A. Forchel, P.A. Knipp, and T.L. Reinecke, “Size dependence
of confined optical modes in photonic quantum dots”, Phys. Rev. Lett. 78,
378-381 (1997).
[5] D. Sanvitto, A. Daraei, A.
Tahraoui, M. Hopkinson, P.W. Fry, D.M. Whittaker and M.S. Skolnick,
“Observation of ultrahigh quality factor in a semiconductor microcavity”, Appl. Phys. Lett. 86, 191109 (2005).
Polycrystalline
opals
In 1995 a group from Ioffe
Institute, St.-Petersburg, Russia, launched synthetic opals [1] as novel 3D
photonic crystals for visible light. This work stimulated world-wide interest
in inverted and functional opals for years to come. For photonic crystal
applications the presence of domains in self-assembled opals is usually
considered as a disadvantage. However the scattering properties of
polycrystalline opals are rather interesting [2] and can be used in a
completely different application connected with developing spatio-spectral
diversity filters [3] for multimode spectroscopy. In this project jointly with DISP group from
References
[1] V.N. Astratov, V.N. Bogomolov,
A.A. Kaplyanskii, A.V. Prokofiev, L.A. Samoilovich, S.M. Samoilovich, and Y.A.
Vlasov, “Optical spectroscopy of opal matrices with CdS embedded in its pores:
quantum confinement and photonic band gap effects”, Nuovo Cimento 17, 1349-1354 (1995).
[2] V.N. Astratov, A.M. Adawi, S.
Fricker, M.S. Skolnick, D.M. Whittaker, and P.N. Pusey, “Interplay of order and
disorder in the optical properties of opal photonic crystals”, Phys. Rev. B 66, 165215 (2002).
[3] Z. Xu, Z. Wang, M.E. Sullivan,
D.J. Brady, S.H. Foulger, and A. Adibi, “Multimodal multiplex spectroscopy
using photonic crystals”, Opt. Express 11,
2126-2133 (2003).