Numerical analysis on the feasibility of a multi-layered dielectric sphere as a three-dimensional photonic crystal

Spherical Bragg resonators for lasing applications: a theoretical approach

This work considers a perfect 3D omnidirectional photonic crystal; Spherical Bragg Resonators (SBR), for lasing applications. We use the recursive transfer matrix method to study scattering in an Er³⁺ doped SBR. We find the threshold gain factor for lasing by scanning poles and zeros of the S-matrix in the complex frequency plane. For a six Si/SiO₂ bilayer SBR, the threshold gain factor corresponds to a dopant density of Er³⁺ of 5.63 × 10²⁰ions/cm³. We believe, our work is the first theoretical demonstration of the ability to engineer optical amplification and threshold gain for lasing in SBRs.

Unified theory of whispering gallery multilayer microspheres with single dipole or active layer sources

The development of a fast and reliable whispering gallery mode (WGM) simulator capable of generating spectra that are comparable with experiment is an important step forward for designing microresonators. We present a new model for generating WGM spectra for multilayer microspheres, which allows for an arbitrary number of concentric dielectric layers, and any number of embedded dipole sources or uniform distributions of dipole sources to be modeled. The mode excitation methods model embedded nanoparticles, or fluorescent dye coatings, from which normalized power spectra with accurate representation of the mode coupling efficiencies can be derived. In each case, the emitted power is expressed conveniently as a function of wavelength, with minimal computational load. The model makes use of the transfer-matrix approach, incorporating improvements to its stability, resulting in a reliable, general set of formulae for calculating whispering gallery mode spectra. In the specific cases of the dielectric microsphere and the single-layer coated microsphere, our model simplifies to confirmed formulae in the literature.

Fabrication of a core–shell–shell particle with a quarter-wave thick shell and its optical properties

In the present work, core–shell–shell particles with quarter-wave thick shells have been synthesized using chemical solution processes for the first time and the optical properties are discussed both theoretically and experimentally.