Er 3+ ‐Doped Lithium Niobate Thin Film: A Material Platform for Ultracompact, Highly Efficient Active Microphotonic Devices

Abstract

Lithium niobate on insulator (LNOI) has already become a promising material platform for ultracompact, high-performance, and low-cost passive microphotonic devices. However, studies on an active LNOI platform are relatively slow. Current work aims at developing an important integrated photonic piece, an active LNOI thin film and waveguide. Herein, it is first demonstrated that a full wafer-scale (3 in. in diameter) Er3+-doped LNOI (Er:LNOI) wafer can be fabricated by directly ion-beam slicing a commercially bulk Er3+-doped lithium niobate wafer. Then, a number of rib-type waveguides with a cross-section <1 μm2 are patterned on its surface using mature nanostructuring technologies. Further optical and spectroscopic characterization results confirm the applicability of the Er:LNOI wafer to the fabrication of an active waveguide. The success in fabrication of Er3+-doped LNOI thin film and waveguides enables the establishment of an active LNOI platform and opens the possibility of developing ultracompact active microphotonic devices, which may find wide applications in the fields of optical communications, nonlinear optics, microwave photonics, and novel photonic systems such as parity-time symmetric systems.