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.
One hotspot of integrated optics is how to realize a highly integrated and high-gain on-chip amplification system in a thin film of lithium niobate on insulator (TFLNOI). Here, a low erbium-doped TFLNOI waveguide amplifier with shorter length is demonstrated using the photolithography-assisted oblique-reactive ion etching technique. A maximum net internal gain of 5.4 dB in the small-signal-gain regime is measured at the peak emission wavelength of 1531.35 nm for a waveguide length of 1.5 mm and an erbium-doped concentration of 0.1 mol. %, indicating a gain per unit length of 36 dB cm−1. This work paves the way for the monolithic integration of diverse active and passive photonic components on the TFLNOI platform.
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