Mid-infrared silicon photonic waveguides and devices [Invited]

TLDR

Silicon photonics is favored for its integration with electronics, high index contrast, small footprint, low cost, and transparency from 1.1 to 8 µm, yet fabrication‑induced parameter variations and high propagation loss limit data‑communication applications, whereas sensing devices tolerate looser controls. This review surveys recent progress in mid‑infrared silicon photonics. The authors examine various platform options, fabrication procedures, benchmark results, and applications to assess the state of the art. Recent advances have produced chip‑based chemical and biological sensors rivaling benchtop instruments, enabled low‑cost, high‑density, multifunctional MIR devices, and are poised to benefit communication, sensing, and nonlinear systems in the coming years.

Abstract

Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics, high index contrast, small footprint, and low cost, as well as its optical transparency in the near-infrared and parts of mid-infrared (MIR) wavelengths (from 1.1 to 8 μm). While considerations of micro- and nano-fabrication-induced device parameter deviations and a higher-than-desirable propagation loss still serve as a bottleneck in many on-chip data communication applications, applications as sensors do not require similar stringent controls. Photonic devices on chips are increasingly being demonstrated for chemical and biological sensing with performance metrics rivaling benchtop instruments and thus promising the potential of portable, handheld, and wearable monitoring of various chemical and biological analytes. In this paper, we review recent advances in MIR silicon photonics research. We discuss the pros and cons of various platforms, the fabrication procedures for building such platforms, and the benchmarks demonstrated so far, together with their applications. Novel device architectures and improved fabrication techniques have paved a viable way for realizing low-cost, high-density, multi-function integrated devices in the MIR. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.