Low‐loss hybrid germanium‐on‐zinc selenide waveguides in the longwave infrared

Abstract

Abstract The longwave infrared (LWIR) range, which spans from 6 µm to 14 µm, is appealing for sensing due to strong molecular fingerprints in this range. However, the limited availability of low‐loss materials that can provide higher‐index waveguiding and lower‐index cladding in the LWIR range presents challenges for integrated photonics. In this work, we introduce a low‐loss germanium‐on‐zinc selenide (GOZ) platform that could serve as a versatile platform for nanophotonics in the LWIR. By bonding high‐quality thin‐film germanium (Ge) to a zinc selenide (ZnSe) substrate, we demonstrate transparency from 2 µm to 14 µm and optical losses of just 1 cm −1 at 7.8 µm. Our results demonstrate that hybrid photonic platforms could be invaluable for overcoming the losses of epitaxially grown materials and could enable a wide range of future quantum and nonlinear photonics.