Loss characterization of waveguides in lithium niobate on insulator

Abstract

Single crystal lithium niobate is a commonly used in optical electronic applications due to its variety of optical effects. However, it is a fairly difficult material to pattern and etching typically induces rough sidewalls. As a result of these limitations, commercial devices are typically use diffusion-type processes which only creates a small index increase. These devices have large footprints and therefore are costly. Lithium niobate on insulator (LNOI) is a technology created to circumvent some of these problems. It consist of a thin film of lithium niobate bonded to an insulating layer, which is then bonded to a host substrate. This allows compact structures due to the higher index confinement achievable. However, propagation loss is still prohibitive, due to the roughness induced by etching processes. We seek to characterize the propagation loss of waveguides in LNOI, and also to reduce the propagation losses.