The quantum cascade laser. A device based on two-dimensional electronic subbands

Abstract

This paper reviews the state-of-the-art of quantum cascade lasers. These new light sources are unipolar semiconductor lasers based on electron resonant tunnelling and optical transitions between quantized conduction band states. Quantum engineering of the electronic energy levels and tailoring of the wavefunctions are used to obtain the correct matrix elements and scattering rates which enable population inversion and the optimization of the overall laser performance. The laser wavelength can be selected over a broad range of the infrared spectrum using the same heterostructure material by tailoring the active layer thickness. Using MBE-grown AlInAs-GaInAs heterostructures, room temperature operation at and has been achieved and lasers in the 4- range were demonstrated at a temperature of 200 K.