Boosted Second Harmonic Generation and Cascaded Sum Frequency Generation from a Surface Crystallized Glass Ceramic Microcavity.

The development of novel materials and structures for efficient second-order nonlinear micro/nano devices remains a significant challenge. In this study, we demonstrate the remarkable enhancement of second-harmonic generation (SHG) and even cascaded sum frequency generation (CSFG) in whispering gallery mode microspheres made of surface-crystallized glass with a 6-μm Ba 2 TiSi 2 O 8 crystal layer. Attributed to the core-shell design, the Ba 2 TiSi 2 O 8 located on the surface can be efficiently coupled with whispering gallery modes, resulting in a highly efficient micron-scale cavity-enhanced second-order optical nonlinearity. Greatly enhanced SHG of the microcavity was observed, which is up to 80 times stronger than that of non-resonant bulk sample. Furthermore, owing to the wavelength non-selectivity of random quasi-phase matching, we demonstrated ultra-wideband SHG with a strong response ranging from 860 nm to 1600 nm and high-contrast polarization characteristics. The glass-ceramic based microsphere cavity also boosts the cascading optical nonlinearity, manifested by a two-magnitude enhancement of CSFG. This work delineates an efficient strategy for boosting nonlinear optical response in glass-ceramics, which will open up new opportunities for applications in photonics and optical communications. This article is protected by copyright. All rights reserved.