Mid- infrared semiconductor laser based trace gas sensor technologies for environmental monitoring and industrial process control

Abstract

Recent advances in the development of compact sensors based on mid-infrared continuous wave (CW), thermoelectrically cooled (TEC) and room temperature operated quantum cascade lasers (QCLs) for the detection, quantification and monitoring of trace gas species and their applications in environmental and industrial process analysis will be reported. These sensors employ a 2f wavelength modulation (WM) technique based on quartz enhanced photoacoustic spectroscopy (QEPAS) that achieves detection sensitivity at the ppb and sub ppb concentration levels. The merits of QEPAS include an ultra-compact, rugged sensing module, with wide dynamic range and immunity to environmental acoustic noise. QCLs are convenient QEPAS excitation sources that permit the targeting of strong fundamental rotational-vibrational transitions which are one to two orders of magnitude more intense in the mid-infrared than overtone transitions in the near infrared spectral region.

Carrier dynamics of type-II InAsSb/GaAsSb W-quantum wells emitting in mid-infrared

“…The exploration of efficient and versatile mid-infrared (MIR) semiconductor emitters has become a focal point in recent years, driven by their expanding applications in open-air communication 1 , environmental monitoring 2,3 , and medical diagnostics 4,5 . The mid-IR spectral range (3-8 micrometers) is pivotal for gas sensing, aligning with molecular absorption bands for the precise detection of gases, pollutants, and biomarkers.…”

A Novel Environmental pressure Compensation Approach of IR Gas Sensors in Industrial environment

“…When the atmospheric pressure alters, the gas per unit volume varies. This in turn affects the spacing between the gas molecules, causing changes in the energy absorbed by the infrared rays [3,4], the concentration of the gas to be tested does not change. So, the tested concentration deviates significantly from the true value and must be corrected for the effect of pressure [5,6].…”

Tunable quantum cascade lasers for midinfrared spectroscopic sensing

“…Compared to the traditional Mid-IR lasers such as CO2 lasers and optical parametric oscillators (OPOs), QCLs offer a coherent source with compact size and broad spectral coverage across the whole Mid-IR region. The narrow linewidth, excellent beam quality, broadband tunability and fingerprint absorption for gas molecules render QCL an indispensable tool in spectroscopy applications [23], including detection of explosives [131,132], medical diagnostics [133,134], industrial process control [135], and environmental monitoring [136]. For multi-gas sensing, QCLs with a broad continuous single-mode tuning range are in great demand.…”