Terahertz quantum cascade lasers

Unipolar semiconductor injection lasers emitting at THz frequencies (from 4.3 THz down to 2.8 THz) 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 75 K (50 K in continuous wave) with several mW of output power and threshold current densities as low as 100 A/cm(2). A promising structure based on an interdigitated cascade is presented that allows operation above 90 K with high emitted powers. (C) 2003 Elsevier B.V. All rights reserved.