Semiconductor laser frequency comb sources such as type-I quantum well cascade diode lasers, interband cascade lasers and quantum cascade lasers have recently shown tremendous potential as spectroscopic sources for chemical sensing. By simultaneously providing broadband coverage and high-spectral resolution in the mid-IR spectral region, they enable detection of large molecules with broadband absorption spectra and small molecules with well-resolved spectral lines. There is a strong interest in technologies that can provide sensitive spectroscopic detection of chemicals using a compact integrated photonics systems, and semiconductor sources offer unique opportunity for system integration. In this paper I will demonstrate results from a dual comb spectroscopy (DCS) systems based on semiconductor sources that effectively down-convert mid-IR spectra to the RF domain where one can perform spectroscopic signal detection followed by chemical concentration retrieval algorithms. We utilize phase and timing correction algorithms to allow for coherent averaging of data generated by free-running lasers over extended time-scales. Examples of high-resolution spectroscopic detection of small and large molecules in a gas phase will be presented. Current limitations and future directions towards fully integrated photonics DCS systems will be discussed.
Gerard Wysocki, "Mid-infrared dual comb spectroscopy with semiconductor frequency comb lasers: progress towards integrated spectroscopic chemical sensors (Conference Presentation)," Proc. SPIE 10922, Smart Photonic and Optoelectronic Integrated Circuits XXI, 109221J (Presented at SPIE OPTO: February 05, 2019; Published: 4 March 2019); https://doi.org/10.1117/12.2510669.6009829773001.
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