Quantum Cascade Laser Spectroscopy for Atmospheric Sensing and Biomedical Diagnostics

Abstract

The invention of quantum cascade laser (QCL) technology rejuvenates the spectroscopic monitoring of trace gas species providing an unprecedented access to the ‘molecular fingerprint region’ covering mid-infrared (mid-IR) spectral range of 3–25 μm. The recent technological advancements of QCL fulfil all the critical parameters as an ideal optical source of a portable and field-deployable mid-IR spectrometer for trace gas analysis in real time. Hence, QCL-based spectroscopic techniques have now widely been employed in various fields covering molecular spectroscopy, atmospheric and environmental trace gas sensing, medical diagnostics, chemical and explosive analysis, industrial process control, and many more. In this chapter, we first discuss various critical features of an optical source for trace gas sensing applications with subsequent brief mention of different mid-IR sources prior to the QCL. Thereafter, the importance of trace gas analysis in environmental and biomedical sciences has been presented in short, followed by a historic overview of QCL. Finally, we focus on the applications of QCL-based spectroscopic techniques in the field of atmospheric and biomedical sciences.