Mid-infrared laser absorption spectroscopy in coiled hollow optical waveguides

Abstract

This study discusses a sensor that relies on innovations in lasers, hollow waveguides, micromachining and microelectronics to provide sensitive and rapid measurements of trace gas concentrations. Quantum cascade (QC) distributed feedback semiconductor lasers in conjunction with unique flexible hollow waveguides that serve as a light guide and gas sample cell to produce a tunable mid-infrared (mid-IR) semiconductor laser absorption spectrometer (MIRLAS). This study uses wavelength modulation spectroscopy to provide measurements that are species specific to assure that measurements are relatively free of interference effects from other constituents of the sample stream. The small sample volumes presented by the hollow waveguide and a proprietary gas exchange mechanism provide for rapid response to gas concentration changes (< 1 s).