Terahertz quantum cascade lasers

Unipolar semiconductor injection lasers emitting at THz frequencies (from View the MathML source down to View the MathML source) are discussed. The devices are based on interminiband transitions in chirped GaAs/AlGaAs superlattices that are arranged in a quantum-cascade scheme. The core, featuring about 100 repetitions of this type of superlattice, is embedded into a novel kind of waveguide loosely based on the surface plasmon concept, which allows low absorption losses and high confinement factors. These devices operate in pulsed mode up to a maximum temperature of View the MathML source (View the MathML source in continuous wave) with several mW of output power and threshold current densities as low as View the MathML source. A promising structure based on an interdigitated cascade is presented that allows operation above View the MathML source with high emitted powers.