Mid-infrared nonlinear optics in thin-film lithium niobate on sapphire

TL;DR

This paper demonstrates efficient mid-infrared frequency conversion using thin-film lithium niobate on sapphire, achieving high transparency and conversion efficiency up to 3.66 μm, advancing integrated nonlinear nanophotonics.

Contribution

It introduces a TFLN-on-sapphire platform with high transparency and efficiency for mid-infrared nonlinear optics, surpassing limitations of silica cladding.

Findings

Mid-infrared light generated up to 3.66 μm.

Normalized efficiencies up to 200%/W-cm².

High transparency of TFLN-on-sapphire up to 4.5 μm.

Abstract

Periodically poled thin-film lithium niobate (TFLN) waveguides have emerged as a leading platform for highly efficient frequency conversion in the near-infrared. However, the commonly used silica bottom-cladding results in high absorption loss at wavelengths beyond 2.5 $\mu$m. In this work, we demonstrate efficient frequency conversion in a TFLN-on-sapphire platform, which features high transparency up to 4.5 $\mu$m. In particular, we report generating mid-infrared light up to 3.66 $\mu$m via difference-frequency generation of a fixed 1-$\mu$m source and a tunable telecom source, with normalized efficiencies up to 200%/W-cm$^2$. These results show TFLN-on-sapphire to be a promising platform for integrated nonlinear nanophotonics in the mid-infrared.