Inter-band cascade lasers, referred to as laser pointers for short, are following near infrared lasers. An important innovative product after the mid-infrared laser, especially in the 3~6μm wavelength field, fills the deficiencies of the DFB laser and QCL. At present, the only manufacturer that can provide an inter-band cascaded ICL laser with any center wavelength between 3000nm and 6000nm. In this wavelength range, most gases have their strongest absorption lines, and the absorption intensity is several orders of magnitude higher than other infrared regions, such as CH4, HCl, CH2O, HBr, CO, CO2, NO, and H2O. ICL lasers have opened up TDLAS ultra-high sensitivity gas sensing applications in the mid-infrared field with innovation. In 1994, the California Institute of Technology’s Jet Propulsion Laboratory first proposed the concept of a second type inter-band cascade laser pointer. The fractured lattice has a large conduction band discontinuity, which can provide very good free carrier confinement, and the lattice constants of GaSb, InAs, and AlSb are very close, which is conducive to growing high-quality materials, so it is very suitable Do the second type of material.
After the concept of the second type was proposed, the theory predicts that it can be lased in continuous wave mode at room temperature, and has a high output power and a low threshold current density. Many research institutions have conducted a lot of research on the second type ICL, including the University of Houston Vacuum Epitaxy Center, the US Naval Laboratory, the US Army Laboratory, and the California Institute of Technology’s Jet Propulsion Laboratory. Until 2012, the first commercial green laser pointer was successful. It was successfully developed by the German nanoplus company and the Würzburg University and other research institutions. It has successfully launched an ICL laser with a wavelength range of 3 to 6 μm in this wavelength range. There are many highly sensitive gas absorption lines, such as CH4, HCl, CH2O, HBr, CO, CO2, NO and H2O, etc. It will bring new applications to laser gas analysis applications.