Recent progress on quantum cascade lasers

Quantum cascade lasers provide coherent radiation in a very wide spectral range, from 4 to 70 /spl mu/m. Performances and applications will be presented and discussed. In these structures, the transition energies, as well as the dipole matrix element and the scattering time can be tailored and optimised by a judicious combination of ultra-thin layers of semiconductor compounds. This approach is the basis for modifying in a unique way the optical and the transport properties of semiconductors, opening avenues for the conception and realisation of artificial materials and useful devices.