Silicon-on-sapphire integrated waveguides for the mid-infrared

TLDR

Silicon nanophotonic waveguides have enabled fully integrated photonic data transmission systems and CMOS‑compatible electronic‑photonic circuits, and their high field confinement supports nonlinear optics, biosensing, and light‑force devices, yet most demonstrations have been confined to near‑infrared wavelengths of 1.1–2 µm. This study aims to demonstrate that single‑mode silicon nano‑waveguides can operate at mid‑infrared wavelengths, specifically at 4.5 µm (2222 cm⁻¹). The authors fabricated and characterized silicon‑on‑sapphire nano‑waveguides, showing single‑mode guidance and low loss at 4.5 µm. The work establishes the first practical integrated silicon waveguide system for the mid‑infrared, opening possibilities for new applications.

Abstract

It has recently been shown that silicon nanophotonic waveguides can be used to construct all of the components of a photonic data transmission system on a single chip. These components can be integrated together with CMOS electronics to create complex electronic-photonic integrated circuits. It has also emerged that the high field confinement of silicon nanoscale guides enables exciting new applications, from chipscale nonlinear optics to biosensors and light-force activated devices. To date, most of the experiments in silicon waveguides have been at wavelengths in the near-infrared, ranging from 1.1-2 microns. Here we show that single-mode silicon nano-waveguides can be used at mid-infrared wavelengths, in particular at 4.5 microns, or 2222.2 1/cm. This idea has appeared in theoretical literature, but experimental realization has been elusive. This result represents the first practical integrated waveguide system for the mid-infrared in silicon, and enables a range of new applications.