Versatile silicon-waveguide supercontinuum for coherent mid-infrared spectroscopy

TL;DR

This paper presents a versatile silicon nanophotonic waveguide platform that generates broad, coherent mid-infrared frequency combs, enabling advanced spectroscopy applications such as molecular fingerprinting and gas detection.

Contribution

It introduces a robust fabrication method and dispersion engineering of silicon waveguides for coherent mid-infrared frequency comb generation spanning 70 THz.

Findings

Achieved broad, coherent frequency combs from 2.5 to 6.2 um

Demonstrated dual-comb spectroscopy at 5 um

Enabled targeted spectral broadening for specific mid-infrared bands

Abstract

Infrared spectroscopy is a powerful tool for basic and applied science. The molecular spectral fingerprints in the 3 um to 20 um region provide a means to uniquely identify molecular structure for fundamental spectroscopy, atmospheric chemistry, trace and hazardous gas detection, and biological microscopy. Driven by such applications, the development of low-noise, coherent laser sources with broad, tunable coverage is a topic of great interest. Laser frequency combs possess a unique combination of precisely defined spectral lines and broad bandwidth that can enable the above-mentioned applications. Here, we leverage robust fabrication and geometrical dispersion engineering of silicon nanophotonic waveguides for coherent frequency comb generation spanning 70 THz in the mid-infrared (2.5 um to 6.2 um). Precise waveguide fabrication provides significant spectral broadening and engineered spectra targeted at specific mid-infrared bands. We use this coherent light source for dual-comb spectroscopy at 5 um.