Tunable diode lasers operate typically between 10 -100 K and their properties, being temperature dependant, require temperature stability within a fraction of a mK. The construction of tunable diode lasers is described together with ways of achieving the operational temperature. Laboratory and field results are discussed for a range of spectral instruments.
Tunable diode laser instruments J.F. Butler and J.O. Sample Tunable diode lasers have recently become available for spectroscopy related applications based on their spectral purity, tunability, high brightness and other features. Used, for example, in spectral absorption measurements, they provide a resolution capability of less than 10 -4 cm -1 , which is orders-of-magnitude better than conventional instruments. Their spectral range of.from less than 3/an to over 30 #m includes infrared signatures of most molecular compounds, providing a basis for a new class of highly sensitive infrared analytical instruments for air pollution monitoring, industrial hazardous gas monitoring, on-line process control, and many other uses.
Tunable diode lasers operate at cryogenic temperatures, typically between 10 K and 100 K. Furthermore, their properties are critically temperature dependent, generally necessitating a temperature stability better than a small fraction of a mK. The achievement of a reliable, moderately priced cryogenic system giving the required performance has been a major factor in the successful development of tunable diode laser instruments. This paper describes the construction, properties and operating characteristics of tunable diode lasers and outlines methods of meeting the operating temperature requirements and trace gas monitoring are discussed and results of both laboratory and field measurements presented.