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 µm. In this work, we demonstrate efficient frequency conversion in a TFLN-on-
sapphire platform, which features high transparency up to 4.5 µm. In particular, we report
generating mid-infrared light up to 3.66 µm via difference-frequency generation of a fixed 1 …