Rejuvenating a Versatile Photonic Material: Thin‐Film Lithium Niobate

Abstract 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.