Lithium niobate on insulator (LNOI) for micro‐photonic devices

Abstract The state‐of‐the‐art of high‐refractive‐index‐contrast single‐crystalline thin lithium niobate (LiNbO 3 ) films as a new platform for high‐density integrated optics is reviewed. Sub‐micrometer thin LiNbO 3 films are obtained by “ion‐slicing”. They can be bonded by two different techniques to a low‐index substrate to obtain “lithium niobate on insulator” (LNOI) even as wafer of 3” diameter. Different micro‐ and nano‐structuring techniques have been used to successfully develop micro‐photonic devices. To be specific, the fabrication and characterization of LNOI photonic wires with cross‐section < 1 µm 2 , periodically poled LNOI photonic wires for second harmonic generation, electro‐optically tunable microring resonators, free standing microrings for hybrid integration, and photonic crystal structures are described.