Gas analysis with infrared molecular gas lasers

Abstract

Infrared spectroscopy is a powerful tool for identification and quantification of functional molecular groups. Molecular gas lasers have long been used for such purposes due to their early development and mature manufacturing technology. Over the past few decades, Quantum Cascade Lasers (QCLs) have popularized due to their continuously tunable wavelength, climbing peak power, and steadily improving manufacturing economics. However, for many applications in the longwave infrared (LWIR) spectral region, carbon dioxide (CO2) lasers retain a clear advantage over QCLs by providing higher power, greater spectral purity and extended coherence length. This combination allows for detection of volatile organic compounds indicative of many diseases such as early-stage lung cancer, an advanced prognosis of which can increase the 5-year survival rate by 37.5%. In addition to medical applications, CO2 lasers also retain their niche in environmental sensing by providing a robust photoacoustic airborne measurement platform for air quality and climate research. Furthermore, recent advances in thermally balanced gas laser architectures have enabled reliable mobile leak monitoring of the insulation gas Sulfur Hexafluoride (SF6) used in medium to ultra-high-voltage electricity transmission lines. With the installed base of SF6 expected to grow 75% by 2030 due to the increase of green energy infrastructure via solar panels and wind turbines – both of which rely on electrical connections, switches, and circuit breakers – this task has gained new urgency due to an upper leak estimate of 15% over the full life cycle of the insulation gas.