Efficient and temperature-tunable second-harmonic generation in a thin film lithium niobate on insulator microdisk

The whispering-gallery-mode microcavities are important in fundamental science and practical applications, which also play an essential role in integrated photonic devices. Here, we prepared a 50 μm diameter thin film lithium niobate on insulator (TFLNOI) microdisk with a Q value of 1.88 × 105 through photolithography-assisted dry-wet etching. Then, we utilize the strong thermo-optic birefringence of TFLNOI to demonstrate the second-harmonic generation (SHG) and highly temperature-tunable SHG in a TFLNOI microdisk resonator, wherein the normalized conversion efficiency of the second harmonic is 140% W−1. Moreover, the tuning slope of spectral tuning is 1.68 nm K−1 for a telecom-band pump. Our device shows great promise for efficient on-chip wavelength conversion to produce highly tunable coherent visible light for broad applications.