Fig. 1. Illustration of the fabrication flow. (a) Microdisk fabrication using a focused ion beam. (b) Chemo-mechanical polishing. (c) Buffered oxide etching corrodes the silica. (d) Fabricated microdisk; the inset is a zoomed-in optical microscope image.

Fig. 2. LTOI experimental setup and optical characterization. (a) The experimental setup for nonlinear processes generated in the LTOI microdisk. VOA, variable optical attenuator. (b) and (c) are the transmission spectrum and Lorentzian fitting of a measured mode around 768.53 nm, respectively.

Fig. 3. Ultraviolet (UV) second-harmonic generation in the LTOI microdisk. (a) The recorded spectrum of the UV SHG signal (around 384.3 nm) is produced by the pump light in the visible band with a different power. (b) The power dependence of the UV SHG signal on the visible fundamental pump. (c) The effective indices as functions of the wavelength, of TE_1,396 in the visible band, and of TE_11,792 in the UV band, where q is the radial mode number and m is the azimuth mode number for TE_q,m. The insets show the simulated mode profiles of the FW and UV SH waves. (d) Intracavity pump power dependency of the generated SH power.