Efficient and scalable edge coupler based on silica planar lightwave circuits and lithium niobate thin films

Recently, lithium niobate on insulator (LNOI) has emerged as a promising photonic integration platform for optical communication due to its outstanding material properties. However, an optical coupler that features high-efficiency is essential to improve the practicability of LN devices. In this work, we proposed a high coupling efficiency and scalable edge coupler, which consists of silica-based planar lightwave circuit (PLC) and LN bilayer taper. The silica-based PLC is positioned on the bottom of LN bilayer taper, which serves as the optical interface connecting the LNOI waveguide to the fiber. The silica-based PLC is interfaced to optical fibers through butt-coupling. Then, LN bilayer taper transfers the light form silica PLC to LN ridge waveguide through adiabatic coupling and converts it gradually into the fundamental mode. When coupled to an ultra-high numerical aperture fiber (UHNA), the simulation results show a low coupling loss of 0.11 dB and 0.128 dB per facet for TE and TM mode, respectively. The scalability of the coupler for large numbers of channels has been proven, which meets the performance requirements of LN devices employed in high-bandwidth, multi-channel systems. These results open a path for lithium niobate photonic integration circuit (PIC) and low-cost optical packaging.

Automated summary

Recently, researchers have proposed a high coupling efficiency and scalable edge coupler for lithium niobate on insulator (LNOI) devices. This coupler consists of a silica-based planar lightwave circuit (PLC) and an LN bilayer taper, which enables efficient optical coupling between LNOI waveguide and fiber. The simulation results demonstrate low coupling losses for both TE and TM modes when coupled to an ultra-high numerical aperture fiber (UHNA), making this coupler suitable for high-bandwidth, multi-channel systems. This innovation paves the way for lithium niobate photonic integration circuit (PIC) and low-cost optical packaging.