Microresonators with whispering gallery modes (WGM) are compact, monolithic, mirrorless resonators with high Q-factors, storing light in a small volume near the periphery of the resonator, guided by total internal reflection. Since a WGM is concentrated near the periphery of the resonator, coating the surface of WGM resonator (WGMR) with a radial
designer RI (refractive index) profile, graded or step index, offers a way to tune the shape of effective optical potential, hence control the properties of modes of the resonator.
In this work, PECVD tool was adapted for the first time to coat optical fibers uniformly to make single layered and Bragg fibers. The deposited films were characterized non-invasively using Mie scattering of films coated on fibers. Additionally, first experimental data on Mie scattering of Bragg fibers has been reported, only relevant work on Bragg coatings being on spheres but limited to theory. Furthermore, anomalous scattering suppression and enhancement from Bragg fiber has been demonstrated and explained, which can be controlled by the design of the Bragg layers. A change in the PBG of the Bragg layers would change the scattering pattern. Backward to forward scattering ratio can also be drastically increased for wide stopband designs as predicted by numerical results. Further, a method for depositing films with speed-dependent refractive index has been introduced. It would be interesting to investigate the chemical composition of the film as a function of rotation speed of the fiber in PECVD to better understand the modified growth kinetics.
This code has a document (161 pages) which describe the algorithm in detail.