Efficient self-imaging grating couplers on a Lithium-Niobate-On-Insulator platform at near-visible and telecom wavelengths

TL;DR

This paper introduces efficient, easily manufacturable self-imaging grating couplers on Lithium-Niobate-On-Insulator platforms, achieving high coupling efficiency at near-visible and telecom wavelengths without metal back-reflectors.

Contribution

The work presents a novel design of self-imaging apodized grating couplers with high efficiency on LNOI, avoiding metal back-reflectors and multi-layer structures.

Findings

Coupling efficiency of ~47.1% at 1550 nm

Coupling efficiency of ~44.9% at 775 nm

No metal back-reflector needed for high directivity

Abstract

Lithium-Niobate-On-Insulator (LNOI) has emerged as a promising platform in the field of integrated photonics. Nonlinear optical processes and fast electro-optic modulation have been reported with outstanding performance in ultra-low loss waveguides. In order to harness the advantages offered by the LNOI technology, suitable fiber-to-chip interconnects operating at different wavelength ranges are demanded. Here we present easily manufacturable, self-imaging apodized grating couplers, featuring a coupling efficiency of the TE0 mode as high as $\simeq 47.1\%$ at $\lambda$=1550 nm and $\simeq 44.9\%$ at $\lambda$=775 nm. Our approach avoids the use of any metal back-reflector for an improved directivity or multi-layer structures for an enhanced grating strength.