Lead salt tunable diode lasers: key devices for high sensitivity gas analysis

Lead salt tunable diode lasers (TDL) are recognised as key components for high sensitivity gas analysis in the mid-infrared. Commercially available device types include double heterostructures, available from 3.0 to 10.8 microns with cw operating temperatures in the range 80 - 180 K, as well as homostructure lasers (4.2 to 25 microns) with lower operating temperatures. Recent developments at Laser Components include the introduction of guaranteed single-mode devices, the extension of overall wavelength coverage, and a series of quality control procedures. These include the now well-established temperature cycling technique, which ensures wavelength stability; an artificial ageing process which simulates long-term storage; and a burn-in procedure which has beneficial effects on long-term laser power stability. Finally, a comprehensive test and characterisation procedure ensures that each laser is optimised for the chosen application. Ongoing studies of long-term laser behaviour and the recent availability of compact, maintenance-free Stirling coolers promise to make lead salt TDLs more attractive for industrial applications in the near future. Pulsed mode operation of lead salt lasers at temperatures of up to 333 K was recently demonstrated.