An Experimental Investigation of Whispering Gallery Mode Microsphere Resonators for Sensing, Lasing, and Nonlinear Optical Applications.

Microsphere resonators are gaining popularity as a key component in photonic circuit devices, optical communications, sensing, lasing, and nonlinear optical applications. As one of the essential categories of optical microcavities, microsphere resonators based on whispering gallery modes (WGMs) have benefits of ultra-high Q factor, small mode volume, ease of fabrication, and low cost. In this paper, we will present experimental results achieved by our group in regards to different application of microsphere resonators:1)We studied the refractometric gas sensing sensitivity and the effect of thickness of the sol-gel silica layer coated to the microsphere to detect small traces of ammonia.2)Rare earth doped microsphere resonators are promising candidates for lasing applications. Tellurite, fluoride, phosphate, and silicate glasses are good hosts for doping with rare earth elements for broadband applications. Tellurite doping with various rare earth elements can provide a wide stimulated emission cross section in the communication band.3)High Q factor and low mode volume of WGM microresonators is a perfect host for non-linear optics application. We will present some non-linear effects which are present in silica spherical microresonators which include stimulated Raman scattering and frequency comb generation via degenerative four wave mixing.