Quantum cascade lasers

Abstract

THz sources are the fundamental requirement for THz technology even for passive detection systems where sources are required for heterodyne detection to improve detectivity. A review is given for one such THz source, the quantum cascade laser. Quantum cascade lasers are unipolar, intersubband photon emitters that can be tuned through the width of quantum wells. Such lasers allow high output powers, up to hundreds of mWs at THz frequencies and provide narrow linewidths ideal for spectroscopic applications. The physics behind the operation of quantum cascade lasers will be reviewed before methods of optimising the laser design for THz operation will be discussed. Present THz performance will be discussed before future performance requirements will be reviewed. © 2014 Springer Science+Business Media Dordrecht.