Long wavelength quantum cascade lasers based on high strain composition

An improved longwave infrared quantum cascade laser, the improvement comprising:

• (a) a highly strained In0.5840Ga0.4160As/Al0.6417In0.3583As composition;
• (b) an active region having 45 stages and emitting at a wavelength of 9 μm;
• (c) an energy spacing E54 of 60 meV;
• (d) an energy spacing EC4 of 430 meV;
• and
• (e) an optical waveguide with 3 μm thick cladding layers adjacent the active region, the cladding layers having a doping level of 2·1016 cm−3, the optical waveguide further having a 4 μm thick top InP layer with a doping level of 5·1016 cm−3 and a 2 μm thick bottom InP layer with a doping level of 5·1016 cm−3, the optical waveguide further having a 1 μm thick plasmon layer with a doping level of 8·1018 cm−3, where the optical waveguide results a free-carrier waveguide loss of 2.1 cm−1 and a mode overlap factor with the active region of 52%.