High-Q Thin-Film Lithium Niobate Microrings Fabricated with Wet Etching

Thin-film lithium niobate (TFLN) has been widely used in electro-optic modulators, acoustic--optic modulators, electro-optic frequency combs, and nonlinear wavelength converters owing to the excellent optical properties of lithium niobate. The performance of these devices is highly dependent on the fabrication quality of TFLN. Although state-of-the-art TFLN microrings with an intrinsic quality factor (Q-factor) exceeding 1 x 10(7) have been realized by inductively coupled plasma-reactive ion etching (ICP-RIE) and chemical mechanical polishing (CMP), ICP-RIE has moderate throughput, moderate reproducibility, and high cost in etching TFLN, while CMP features moderate throughput and low cost in etching TFLN. Here, a wet etching method for TFLN, leading to the fabrication of a micro-racetrack with an intrinsic Q-factor of over 9.27 x 10(6) is developed. The suitability of this method to fabricate a narrow coupling gap between the bus waveguide and microring enables the coupling conditions of the microring to be customized. This method features a high throughput, a high reproducibility, and a low cost in etching TFLN, showing the potential to boost the mass production of integrated LN photonic devices with high fidelity and affordability dramatically.

Automated summary

Thin-film lithium niobate (TFLN) has excellent optical properties and is widely used in various electro-optic and acousto-optic devices. This study developed a wet etching method for TFLN, enabling the fabrication of high-quality micro-racetracks with customized coupling conditions. The method offers high throughput, reproducibility, and cost-efficiency, showing great potential for mass production of integrated LN photonic devices.