Silicon photonic platforms for mid-infrared applications [Invited]

TLDR

Silicon photonic integrated circuits, already mature for telecom and data‑center use, are now being scaled to the short mid‑infrared (2–4 µm) range, prompting research into diverse material platforms such as SOI, silicon nitride, germanium, sapphire, SiGe, and aluminum nitride to achieve low‑loss waveguides for applications from lab‑on‑chip sensors to free‑space communications. The paper reviews current silicon‑MIR photonics achievements, presents the authors’ own platform development, discusses integration strategies and remaining device challenges, and outlines future research directions. The authors conduct a comprehensive review of silicon‑MIR photonic devices across multiple material platforms, detail their own platform development, analyze integration schemes and challenges, and illustrate application examples such as gas sensors.

Abstract

Silicon photonic integrated circuits for telecommunication and data centers have been well studied in the past decade, and now most related efforts have been progressing toward commercialization. Scaling up the silicon-on-insulator (SOI)-based device dimensions in order to extend the operation wavelength to the short mid-infrared (MIR) range (2–4 μm) is attracting research interest, owing to the host of potential applications in lab-on-chip sensors, free space communications, and much more. Other material systems and technology platforms, including silicon-on-silicon nitride, germanium-on-silicon, germanium-on-SOI, germanium-on-silicon nitride, sapphire-on-silicon, SiGe alloy-on-silicon, and aluminum nitride-on-insulator are explored as well in order to realize low-loss waveguide devices for different MIR wavelengths. In this paper, we will comprehensively review silicon photonics for MIR applications, with regard to the state-of-the-art achievements from various device demonstrations in different material platforms by various groups. We will then introduce in detail of our institute’s research and development efforts on the MIR photonic platforms as one case study. Meanwhile, we will discuss the integration schemes along with remaining challenges in devices (e.g., light source) and integration. A few application-oriented examples will be examined to illustrate the issues needing a critical solution toward the final production path (e.g., gas sensors). Finally, we will provide our assessment of the outlook of potential future research topics and engineering challenges along with opportunities.