Accurate analysis of electromagnetic fields evolution in whispering gallery (WG) mode resonator with time dependent material parameters is presented. The excited fields are described by means of a rigorous mathematical approach that is based on the analytical solution in the Laplace transform domain and accurate evaluation of residues at singular points of the obtained functions. Transient response of WG mode on a sole time switching material parameters as well as on a pulse and packet of pulses are considered.
IntroductionOptical resonators have been attracting increasing attention recently due to their potential in a variety of scientific and engineering applications including low-threshold lasers [1], ultra-small filters [2] and miniature biosensors [3,4]. In the simplest cases, such resonators have the shape of a thin disk, a ring or a sphere. In the vicinity of a curved surface whispering gallery (WG) modes can be excited due to almost total internal reflection of the light. Quality (Q) factor of these oscillations are extremely high because light becomes trapped within the resonator.Dynamic resonators and photonic systems, in which material parameters can be varied by external forces, have pronounced benefit for their use in all-optical switchers and tunable filters [5] and represent a powerful approach for all-optical control of light. Permittivity modulation within microcavity systems can be exploited to stop, store and time-reverse of light pulse [6]. Modulation of permittivity in photonic crystals leads to changes of light colour [7] and reversed Doppler shifts [8]. Dynamic control of photonic bandgap can be used to coherently convert a propagating light pulse into stationary excitation which is effectively trapped in the medium [9]. Tuning in time of the refractive index can be used to realize fast frequency shift in linear material microcavity in photonic crystal [10] or dynamic WG mode N. Sakhnenko ( )