Faist J Ajili L Scalari G Giovannini M Beck M Rochat M Beere H Davies AG Linfield EH Ritchie D 2004 Recent developments in terahertz quantum cascade lasers are reviewed. Structures operating from a wavelength of lambda = 66 microm down to lambda = 87 microm are demonstrated. These devices used either a three-quantum-well chirped-superlattice active region or an active region based on a bound-to-continuum transition. The comparison between structures grown in a waveguide based on a single interface plasmon and a buried contact and (non-lasing) structures using a double plasmon waveguide demonstrates the importance of waveguide design on the operation of such devices. Continuous-wave operation up to a maximum temperature of 55 K with up to 15 mW output power at 10 K was demonstrated. https://sonar.ch/global/documents/259998 eng info:eu-repo/semantics/altIdentifier/doi/10.1098/rsta.2003.1313 info:eu-repo/semantics/altIdentifier/pmid/15306516 Philosophical transactions. Series A, Mathematical, physical, and engineering sciences. - 2004 General Engineering General Physics and Astronomy General Mathematics Terahertz quantum cascade lasers. http://purl.org/coar/resource_type/c_6501