Sensitive Chemical Detection with Distributed Feedback Interband Cascade Lasers

Abstract

Abstract The hybrid architecture of the interband cascade laser (ICL) combines the interband active transitions of a conventional diode laser with the multiple active stages of a quantum cascade laser (QCL). An advantage for spectroscopic applications is its much lower power dissipation than other sources such as the QCL at mid‐infrared (IR) wavelengths spanning 3–6 µm. Distributed‐feedback (DFB) ICLs emitting in a single spectral mode have been developed using both top‐grating and lateral‐grating geometries. The top‐grating approach has produced up to 28 mW of continuous wave (CW) power in a single spectral mode. Lateral‐grating DFB ICLs have produced single‐mode output throughout the 3–6 µm spectral region, often operating with drive powers <100 mW. Some of the most important extractive and in situ measurement techniques for laser‐based gas sensing are described, including direct absorption spectroscopy (DAS), wavelength modulation spectroscopy (WMS), quartz enhanced photo‐acoustic spectroscopy (QEPAS), and off‐axis integrated cavity output spectroscopy (OA‐ICOS). We review a number of applications of ICL‐based systems to the sensing of methane, ethane, formaldehyde, and sulfur dioxide.