Abstract

Semiconductor diode lasers, including lead salt lasers operating at wavelengths beyond 3 μm and InGaAlP, GaAlAs, or InGaAsP lasers operating at wavelengths less than 2 μm, have been used extensively for measurement of trace gases by optical absorption.¹ The inherently narrow linewidths of these light sources, combined with high sensitivity detection techniques such as wavelength modulation spectroscopy² or frequency modulation spectroscopy,³ provides a capability for the highly selective and sensitive measurement of a wide range of species important in atmospheric and combustion research, environmental monitoring, and process monitoring. The lead salt lasers, accessing vibrational fundamental bands, generally permit the highest detection sensitivity. However, development of commercial diode laser-based instrumentation for environmental or industrial application has focused on the use of the near-infrared wavelength devices due to their characteristics of room temperature operation, compatibility with silica optical fibers, and availability of single mode operating devices.

© 1998 Optical Society of America