Low-threshold lasing in active opal photonic crystals

We theoretically study a low-threshold band-edge lasing in three-dimensional photonic crystals (PhCs) with a face-centered cubic lattice structure, using a complex-valued permittivity approach combined with the Korringa-Kohn-Rostoker method. We show that the lasing threshold at the low-frequency band edge is smaller than that at the high-frequency band edge for the first-order stop band of the PhC. We also analyze the impact of the number of the PhC's layers on the frequency of band-edge lasing and the lasing threshold near the first-order stop band in the GL direction, and demonstrate a broad tunability of the lasing frequency with change in the emission collection angle. The obtained results are beneficial for the performance enhancement of tunable, PhC-based chip lasers. (C) 2013 Optical Society of Americ

Low-threshold lasing in photonic-crystal heterostructures

We study a photonic crystal (PhC) heterostructure cavity consisting of gain medium in a three-dimensional (3D) PhC sandwiched between two identical passive multilayers. For this structure, based on Korringa-Kohn-Rostoker method, we observe a decrease in the lasing threshold of two orders of magnitude, as compared with a stand-alone 3D PhC. We attribute this remarkable decrease in threshold gain to the overlap of the defect cavity mode with the reduced group velocity region of the PhC's dispersion, and the associated enhancement in the distributed feedback from the ordered layers of the PhC. The obtained results show the potency for designing PhC-based, compact on-chip lasers with ultra-low thresholds. (C) 2014 Optical Society of Americ

Spatial and spectral distributions of emission from dye-doped photonic crystals in reflection and transmission geometries

Spectral distribution of emission was measured in a large angular range (8 deg to 180 deg) around a self-assembled photonic crystal synthesized from colloids of Rhodamine-B dye-doped polystyrene. Its comparison with the emission from the same dye-doped colloids in a liquid suspension provides a better understanding of the anisotropic propagation of light within the structure due to its pseudo-gap properties. The spontaneous emission is suppressed by 40% in the presence of the stop band over a large bandwidth (similar to 50%) of the first-order bandgap in the Gamma L direction, due to the appropriate choice of the colloidal diameter. Spectral shifts in the spontaneous emission spectrum occur with the variation in the detection angle. The inevitable disorder in the self-assembled crystals and the resultant effect on emission was modeled by comparing the experimentally obtained reflection spectrum with the band structure calculated using the Korringa-Kohn-Rostoker method to exclude finite-size effects. Reflection and transmission are complementary because of the absence of strong absorptive effects. The extent of redistribution in the emission from a photonic crystalline environment with respect to a homogeneous emitter is significant in the spectral and spatial domains. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JNP.6.063526

Analysis of Lasing in Dye-Doped Photonic Crystals

Recently, we experimentally demonstrated room-temperature lasing of self-assembled opal photonic crystal (PhC) made of rhodamine-B-doped polystyrene colloids. Here, we explain this experimental observations by analyzing the phenomenon of light amplification in dye-activated PhCs via a complex-valued permittivity of the colloids. We show that the lasing is facilitated by the enhanced distributed feedback due to the reduced group velocity in the vicinity of the photonic band edge. This simple approach to the analysis of PhC lasing behavior allows us to calculate the lasing wavelength in close agreement with the experimental value. It also enables the estimation of gain coefficient required for lasing and may prove useful in design of compact PhC-based lasers

Chiral nanoparticles in singular light fields

The studying of how twisted light interacts with chiral matter on the nanoscale is paramount for tackling the challenging task of optomechanical separation of nanoparticle enantiomers, whose solution can revolutionize the entire pharmaceutical industry. Here we calculate optical forces and torques exerted on chiral nanoparticles by Laguerre–Gaussian beams carrying a topological charge. We show that regardless of the beam polarization, the nanoparticles are exposed to both chiral and achiral forces with nonzero reactive and dissipative components. Longitudinally polarized beams are found to produce chirality densities that can be 10(9) times higher than those of transversely polarized beams and that are comparable to the chirality densities of beams polarized circularly. Our results and analytical expressions prove useful in designing new strategies for mechanical separation of chiral nanoobjects with the help of highly focussed beams

Strongly modified plasmon-matter interaction with mesoscopic quantum emitters

Semiconductor quantum dots (QDs) provide an essential link between light and matter in emerging fields such as light-harvesting, all-solid-state quantum communication, and quantum computing. QDs are excellent single-photon sources and can store quantum bits for extended periods making them promising interconnects between light and matter in integrated quantum information networks. To this end the light-matter interaction strength must be strongly enhanced using nanophotonic structures such as photonic crystal cavities and waveguides or plasmonic nanowires. So far it has been assumed that QDs can be treated just like atomic photon emitters where the spatial properties of the wavefunction can be safely ignored. Here we demonstrate that the point-emitter description for QDs near plasmonic nanostructures breaks down. We observe that the QDs can excite plasmons eight times more efficiently depending on their orientation due to their mesoscopic character. Either enhancement or suppresion of the rate of plasmon excitation is observed depending on the geometry of the plasmonic nanostructure in full agreement with a new theory. This discovery has no equivalence in atomic systems and paves the way for novel nanophotonic devices that exploit the extended size of QDs as a resource for increasing the light-matter interaction strength.Comment: 9 pages, 4 figure