Quantum cascade laser intracavity absorption spectrometer for trace gas sensing

Abstract

A mid-infrared intracavity laser absorption spectrometer for trace gas sensing is demonstrated. An external-cavity multi-mode quantum cascade laser with central wavelength 8.0 μm was combined with a scanning Fabry-Perot interferometer, which analyzed the change of the laser emission spectrum caused by introducing an analyte inside the cavity. The detection mechanism is based on monitoring the laser spectrum dynamics at adiabatically changing laser conditions in long pulse operation mode. Fast acquisition and vapor exchange allow nearly real-time analyte detection. Sensitivity at the level of 1 × 10−5 cm−1 was demonstrated based on a weak water vapor absorption line.

Tunable single-mode slot waveguide quantum cascade lasers

“…[3][4][5][6] Because many gases have their "fingerprint regions" in the mid-infrared range, QCLs are the ideal mid-infrared radiation sources for various sensing and spectroscopy applications. [7][8][9] Short-distance free space communication will also benefit from using QCLs due to the reduced Mie scattering losses. 10 For practical applications such as spectroscopy, singlemode QCLs are more advantageous owing to the much reduced laser linewidth.…”