Nonlinear Effects In Ultra-high-Q Whispering-Gallery Optical Microspheres

High-(?) optical microcavities confine light at resonant frequencies for extended periods of time and fundamentally alter the interaction of light with matter. They are the basis of numerous applied and fundamental studies, such as cavity (?)ED, photonics and sensing. Of all resonant geometries, surface tension-induced microcavities, such as silica micro-spheres, exhibit the highest (?)-factor to date of nearly 9 billion. Despite this high (?)-factor and the intense interest in these structures, the nonlinear optical properties of silica micro-spheres have remained nearly entirely unexplored. In this thesis, one of the nonlinear optical phenomenas which can occur in ultra-high-(?) microspheres is investigated.It is found, four-wave mixing can occur in taper fiber coupled silica micro-spheres at threshold levels typically in the micro-Watt range. To efficiently exite the whispering-gallery modes, tapered optical fibers in these experiments are used to pump WGMs. The quality factor (?) of microspheres can be obtained through the results. In adittion, the tapered optical fiber functions to extract the nonlinear effects. The efficient tapered-fiber coupling junction enables to the extrcting of the Kerr-FWM in the silica micro-spheres with high (?) measured. When operating at high powers required for FWM, thermal effects can occur in microspheres with high pump energy which can result in detrimental effects to the process. So we implanted a PID lockbox to lock a whispering-gallery resonance of a fused-silica microsphere to a laser.