Quantum Cascade Lasers for the Mid-infrared Spectral Range: Devices and Applications

Abstract

Quantum cascade lasers emitting at lambdasim5 �m based on differentactive region designs are investigated. Using lattice-matched GaInAs/AlInAson InP substrates the maximum peak optical power as well as the maximumpulsed-mode operating temperature is enhanced by incorporating AlAsblocking barriers together with strain-compensating InAs layers intothe active regions. Further improvement is achieved by employingstrain-compensated GaInAs/AlInAs quantum wells for which maximumpulsed-mode operating temperatures in excess of 350 K are observed.High-reflectivity coated devices mounted substrate-side down showa maximum continuous-wave operating temperature of 194 K. Also thenormalized relative intensity noise is investigated. Finally, a comparisontrace-gas sensing experiment employing one of the present quantumcascade lasers and a lead-chalcogenide laser is presented. Detectingthe P(25) absorption line of CO, higher stability is obtained usinga quantum cascade laser.