Optical Parametric Oscillators In Whispering Gallery Mode Resonators Based On Dielectric Superlatice

Whispering gallery mode (WGM) resonators have versatile applications in nonlinear optics. Dramatically enhancement of light intensity in WGM resonators can be achieved due to their small mode volume and high quality factor. We demonstrated optical parametric oscillators in crystalline WGM resonators (WGMOPO) made from lithium niobate (LiNbO3) and lithium tantalite (LiTaO3) with quality factor over 107. Combining with quasi-phase-matching(QPM) techniques, we achieved optical parametric oscillators with ultra-low threshold and ultra-wide tuning range in periodically poled congruently grown lithium tantalite (PPCLT) WGM resonators. Our research shows this kind of resonators has great potential for compact, widely tunable and narrow linewidth mid-infrared laser source. The main content in this paper includes:1. Firstly, we developed a set of technologies for fabricating and testing WGM resonators based on crystalline lithium niobate and lithium tantalite. By a series of carefully polishing procedures, we achieved WGM resonators with quality factor over 107 from LiNbO3 and LiTaO3 crystals.2. We designed a new kind of WGM resonators based on periodically poled structure. Both the theory and experimental results indicate that the period in WGM resonators with this kind poling pattern is chirped when light travels around the resonators, hence the effective poling period varies from A to 1.2A3. The technique of optical parametric oscillation in WGM resonators was studied. Combing with quasi-phase-matching technique, we achieved mid-infrared OPO with low threshold (<2 mW) and high conversion efficiency (>50%). According to our theory and experimental results, this kind of OPO can have a ultra-wide tuning range from 1.7μm to 3 μm in a single sample.