Interband cascade laser information

Interband cascade lasers (ICLs) are a type of laser diode that can produce coherent radiation over a large part of the mid-infrared region of the electromagnetic spectrum. They are fabricated from epitaxially-grown semiconductor heterostructures composed of layers of indium arsenide (InAs), gallium antimonide (GaSb), aluminum antimonide (AlSb), and related alloys. These lasers are similar to quantum cascade lasers (QCLs) in several ways. Like QCLs, ICLs employ the concept of bandstructure engineering to achieve an optimized laser design and reuse injected electrons to emit multiple photons. However, in ICLs, photons are generated with interband transitions, rather than the intersubband transitions used in QCLs. Consequently, the rate at which the carriers injected into the upper laser subband thermally relax to the lower subband is determined by interband Auger, radiative, and Shockley-Read carrier recombination. These processes typically occur on a much slower time scale than the longitudinal optical phonon interactions that mediates the intersubband relaxation of injected electrons in mid-IR QCLs. The use of interband transitions allows laser action in ICLs to be achieved at lower electrical input powers than is possible with QCLs.

The basic concept of an ICL was proposed by Rui Q. Yang in 1994.^[1] The key insight he had was that the incorporation of a type-II heterostructure similar to those used in interband resonant tunneling diodes would facilitate the possibility of cascade lasers that use interband transitions for photon generation. Further improvement to the design and development of the technology was carried out by Yang and his collaborators at several institutions, as well as by groups at the Naval Research Laboratory and other institutions. ICLs lasing in continuous wave (cw) mode at room temperature were first demonstrated in 2008. This laser had an emission wavelength of 3.75 μm.^[2] Subsequently, cw operation of ICLs at room temperature has been demonstrated with emission wavelengths ranging from 2.9 μm to 5.7 μm.^[3] ICLs at cooler temperatures have been demonstrated with emission wavelengths between 2.7 μm to 11.2 μm.^[4] ICLs operating in cw mode at ambient temperature are able to achieve lasing at much lower input powers than competing mid-IR semiconductor laser technologies.^[5]