Abstract

By controlling the quantum well widths and the tunnelling barrier thickness of heterostructures it is possible to create artificial potentials where level separations, dipole matrix elements, lifetimes and scattering times are dependent on the potential design. This allows us to conceive new materials (material by design) where electronic and optical properties can be tailored not only for demonstrate new physical effects but also to optimise device performance. The Quantum Cascade (QC) laser is an excellent example of how quantum engineering can be used to design and develop new laser material in the mid-ir. After the first demonstration of Quantum cascade lasers a strong effort has been done to improve the performance of this mid-ir source which is now ready to be exploited into sensing systems for molecular detection in the atmospheric windows (3 - 5 µm and 8 - 13 µm). Room temperature operation^1,2, high peak power² and DFB lasers⁴ have been demonstrated, making this laser the first room temperature mid-ir coherent semiconductor source operating single mode in the 5 - 9 µm range.

© 1998 IEEE