On optical forces in spherical whispering gallery mode resonators.

In this paper we discuss the force exerted by the field of an optical cavity on a polarizable dipole. We show that the modification of the cavity modes due to interaction with the dipole significantly alters the properties of the force. In particular, all components of the force are found to be non-conservative, and cannot, therefore, be derived from a potential energy. We also suggest a simple generalization of the standard formulas for the optical force on the dipole, which reproduces the results of calculations based on the Maxwell stress tensor.

Luminescence properties of a Fibonacci photonic quasicrystal.

An active one-dimensional Fibonacci photonic quasi-crystal is realized via spin coating. Luminescence properties of an organic dye embedded in the quasi-crystal are studied experimentally and compared to theoretical simulations. The luminescence occurs via the pseudo-bandedge mode and follows the dispersion properties of the Fibonacci crystal. Time resolved luminescence measurement of the active structure shows faster spontaneous emission rate, indicating the effect of the large photon densities available at the bandedge due to the presence of critically localized states. The experimental results are in good agreement with the theoretical calculations for steady-state luminescence spectra.

Radiative energy transfer in disordered photonic crystals.

The difficulty of description of the radiative transfer in disordered photonic crystals arises from the necessity to consider on an equal footing the wave scattering by periodic modulations of the dielectric function and by its random inhomogeneities. We resolve this difficulty by approaching this problem from the standpoint of the general multiple scattering theory in media with an arbitrary regular profile of the dielectric function. We use the general asymptotic solution of the Bethe-Salpeter equation in order to show that for a sufficiently weak disorder the diffusion limit in disordered photonic crystals is presented by incoherent superpositions of the modes of the ideal structure with weights inversely proportional to the respective group velocities. The radiative transfer and the diffusion equations are derived as a relaxation of long scale deviations from this limiting distribution. In particular, it is shown that in general the diffusion is anisotropic unless the crystal has sufficiently rich symmetry, say, the square lattice in 2D or the cubic lattice in 3D. In this case, the diffusion is isotropic and only in this case can the effect of the disorder be characterized by a single mean free path depending on frequency.

Nonlinear thermal effects in optical microspheres at different wavelength sweeping speeds.

Results of detailed experimental investigations of the power and sweeping speed dependent resonance bandwidth and resonance wavelength shift in microsphere resonators are presented. The experimental manifestations of the nonlinear effects for the different sweeping modes are considered and a possibility of separation between the Kerr and thermal nonlinearities is discussed. As it follows from the detailed comparison between theory and experiments, a single mode theoretical model, based on the mean field approximation, gives a satisfactory description of the experimental data only at small coupling powers and fast sweeping. For example, the values of Kerr nonlinearity, obtained through the fitting of the experimental data, are far from the expected, commonly used ones.

Photonic band mixing in linear chains of optically coupled microspheres.

The paper deals with optical excitations arising in a one-dimensional chain of identical spheres due to optical coupling of whispering gallery modes (WGM). The band structure of these excitations depends significantly on the intermixing between WGMs characterized by different values of angular quantum number, l. We develop a general theory of the photonic band structure of these excitations taking these effects into account and applied it to several cases of recent experimental interest. In the case of bands originating from WGMs with the angular quantum number of the same parity, the calculated dispersion laws are in good qualitative agreement with recent experiment results. Bands resulting from hybridization of excitations resulting from whispering gallery modes with different parity of l exhibits anomalous dispersion properties characterized by a gap in the allowed values of wave numbers and divergence of group velocity.

Effects of spatial nonuniformity on laser dynamics.

Semiclassical equations of lasing dynamics are rederived for a lasing medium in a cavity with a spatially nonuniform dielectric constant. The nonuniformity causes a radiative coupling between modes of the empty cavity, which results in a renormalization of self- and cross-saturation coefficients. Possible manifestations of these effects in random lasers are discussed.

Scaling and the center-of-band anomaly in a one-dimensional Anderson model with diagonal disorder.

We resolve the problem of the violation of single parameter scaling at the zero energy of the Anderson tight-binding model with diagonal disorder. It follows from the symmetry properties of the tight-binding Hamiltonian that this spectral point is, in fact, a boundary between two adjacent bands. The states in the vicinity of this energy behave similarly to states at other band boundaries, which are known to violate single parameter scaling.

Scaling in the one-dimensional anderson localization problem in the region of fluctuation states.

We numerically study the distribution function of the conductivity (transmission) in the one-dimensional tight-binding Anderson model in the region of fluctuation states. We show that while single parameter scaling in this region is not valid, the distribution can still be described within a scaling approach based upon the ratio of two fundamental quantities, the localization length, l(loc), and a new length, l(s), related to the integral density of states. In an intermediate interval of the system's length L, l(loc)<

Polariton local states in periodic Bragg multiple-quantum-well structures.

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.