# High coupling efficiency grating couplers on lithium niobate on insulator

## TL;DR

This paper presents highly efficient monolithic grating couplers on lithium niobate on insulator, achieving significant coupling efficiencies for TE and TM polarizations, with exploration of taperless designs for compactness.

## Contribution

The work introduces monolithically defined grating couplers on lithium niobate on insulator with high coupling efficiency and investigates taperless designs for improved compactness.

## Key findings

- Coupling efficiency of 44.6% for TE polarization.
- Coupling efficiency of 19.4% for TM polarization.
- Taperless grating couplers enable more compact device designs.

## Abstract

We demonstrate monolithically defined grating couplers in $Z$-cut lithium niobate on insulator for efficient vertical coupling between an optical fiber and a single mode waveguide. The grating couplers exhibit $\sim 44.6\%$/coupler and $\sim 19.4\%$/coupler coupling efficiency for TE and TM polarized light respectively. Taperless grating couplers are investigated to realize a more compact design.