Mid-infrared (Mid-IR) range (i.e. the spectral window 2.5—10 μm) is considered as the golden mine for molecular spectroscopy, where most materials feature strong absorptions due to molecular transitions, e.g. hydrogen bonds (N-H, O-H and C-H) show absorptions in the range 2.5—4.0 μm (4000—2500 cm-1), and the absorption strengths are usually 10 to 1000 times greater than those in the visible and near-infrared ranges. Triggered by a significant number of applications such as pharmaceutical, environmental or medical breath analysis, mid-IR spectroscopy has attracted substantial attention in the past decade. The development of mid-IR spectroscopy is mainly focusing on the creation of robust and coherent mid-IR sources, while a compact and simple system configuration is also required for potential applications beyond the laboratory frame.
MIRCOMB aimed to demonstrate a coherent and broadband mid-IR frequency comb based on integrated and compatible photonic platforms. A mid-IR frequency comb is a series of lasers with equal spacing between frequencies in the mid-infrared range. The innovative approach was to transplant the Kerr frequency comb technology into the mid-IR spectral range, which enables coherent optical frequency combs with high compactness. This approach was invented by the host EPFL group and has found great success in the near-infrared telecommunication range in the past decade, but still remains quite unexplored in the mid-IR range. Moreover, we have investigated the approach of photonic chip-based coherent supercontinuum process that also represents an efficient and compact solution to the mid-IR frequency comb generation. The project consists of two primary phases: (phase I) mid-IR frequency comb generation in photonic chip-based silicon nitride platform; and (phase II) mid-IR dual comb spectroscopy.
