On-chip ultraviolet second-harmonic generation in lithium-tantalate thin film microdisk

The compact and reliable ultraviolet [UV) source has attracted remarkable attention for its potential use in optical measurement systems, high-density optical storage, and biomedical applications. We demonstrate ultraviolet generation by frequency doubling in a lithium-tantalate-on-insulator [LTOI) microdisk via modal phase matching. The 50-μm-diameter microdisk was milled by a focused ion beam [FIB) and followed by chemo-mechanical polishing [CMP) to smooth the disk surface and edge, and the Q-factor reaches 2.74 × 105in the visible band. On-chip UV coherent light with a wavelength of384.3 nm was achieved, which shows great promise for using LTOIs in integrated ultraviolet source platforms.