Practical laser sources will unlock important applications in the mid-IR

Abstract

The mid-IR spectral region is increasingly important for a wide range of applications in the industrial, environmental, security, medical, and scientific sectors. Examples include sensing and spectroscopy; biomedical imaging and tissue processing; industrial monitoring and process control; materials processing; and trace molecular detection for environmental study and security. These applications represent a vast array of different source requirements in tunability and energy. But all are limited in some way by current laser source format and availability. A number of approaches have been effected to address these limitations, such as lead-salt lasers, high-power diode-pumped solid-state lasers, quantum cascade lasers (QCLs), and optical parametric oscillators. Many of these systems require multistage resonators, complex growth and processing, or cryogenic cooling to achieve significant performance and/or tunability. The most significant developments have been, and so far continue to be, in QCLs. For instance, in the GaInAs/AlInAs-on-InP (gallium indium arsenide/aluminum indium arsenide on indium phosphide) material system, an impressive wavelength coverage over 3.5-12 m has been demonstrated, with output powers in excess of 1W over most of this range. Current research and development challenges seek to extend the spectral coverage to shorter wavelengths while increasing power efficiency. Optically pumped semiconductor disk lasers (SDLs) 1-3 based on InGaAs/(Al)GaAs and (AlGaIn)(AsSb, arsenic antimonide), emitting in the 1 and 2 m spectral ranges, respectively, are among the powerful technologies to have emerged. These lasers provide high beam quality, continuous-wave outputs with