Progress toward 3–5μm strained quantum cascade laser design using quasi-phased matched non-linear conversion on GaAs (111)B

Typical infrared quantum cascade laser (QCL) designs focus on the high-mid and far-infrared regions due to the small intersubband spacing achievable using near lattice matched systems - GaAs/AlGaAs, GaSb/AlAb, GaInAs/GaInSb/InP, etc. Requirements for shorter wavelengths, 3-30μm, force designers to choose laser designs using band-to-band transitions (Type I). Using these designs, it is difficult to achieve high-efficiency allowing for room temperature continuous wave operation due to inherent losses associated with Auger recombination. One potential solution to this problem is to intentionally incorporate non-lattice matched (strained) materials into the laser design. In the case of GaAs based QCLs, incorporation of indium into the well regions increases the electron affinity, thereby increasing the achievable barrier height and allowing for larger intersubband transitions.