Cavity-Enhanced Vernier Spectroscopy with a Chip-Scale Mid-Infrared Frequency Comb

Lukasz A. Sterczewski*, Tzu Ling Chen, Douglas C. Ober, Charles R. Markus, Chadwick L. Canedy, Igor Vurgaftman, Clifford Frez, Jerry R. Meyer, Mitchio Okumura, Mahmood Bagheri

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Chip-scale optical frequency combs can provide broadband spectroscopy for diagnosing complex organic molecules. They are also promising as miniaturized laser spectrometers in applications ranging from atmospheric chemistry to geological science and the search for extraterrestrial life. While optical cavities are commonly used to boost sensitivity, it is challenging to realize a compact cavity-enhanced comb-based spectrometer. Here, we apply the Vernier technique to free-running operation of an interband cascade laser frequency comb in a simple linear geometry that performs cavity-enhanced chemical sensing. A centimeter-scale high-finesse cavity simultaneously provides selective mode filtering and enhancement of the path length to 30 m. As a proof-of-concept, we sense transient open-path releases of ppm-level difluoroethane with 2 ms temporal resolution over a 1 THz optical bandwidth centered at 3.64 μm. The sub-MHz comb teeth width governs the optical resolution, while the ?9.7 GHz comb repetition rate determines the optical sampling grid. The minimum detectable absorption reaches 4.3 × 10-2 at 300 ms.

Original languageEnglish
Pages (from-to)994-1001
Number of pages8
JournalACS Photonics
Issue number3
StatePublished - 16 Mar 2022


  • cavity-enhanced
  • frequency comb
  • interband cascade laser
  • mid-infrared
  • Vernier spectroscopy


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