Rejuvenating a Versatile Photonic Material: Thin-Film Lithium Niobate

The excellent optical and unique material properties of lithium niobate have long established it as a prevailing photonic material, especially for the long-haul telecom modulator and wavelength-converter applications. However, conventional lithium niobate optical waveguides are bulky, hence large-scale photonic circuit implementations are impeded and high power requirements are imposed. To address these shortcomings, thin-film lithium niobate technology has been a topic of intense research in the last few years and a plethora of ultracompact devices with significantly superior performances than the conventional counterparts have been demonstrated. These efforts have rejuvenated lithium niobate for novel electro-, nonlinear-, and quantum-optic applications. Herein, the most recent advancements of this booming field are summarized and a perspective for future directions is given.