COMMENTS ON QUANTUM CASCADE LASERS

Quantum cascade lasers are new unipolar light sources based on electro n resonant tunneling and optical transitions between quantized conduct ion band states. Quantum engineering of the electronic energy levels, wavefunctions, matrix elements and scattering rates is used to design population inversion and optimize laser gain and overall performance. The wave-length can be selected over a broad range of the infrared spe ctrum using the same heterostructure material by tailoring the active layer thickness. High power loom temperture operation at 5 and 8.5 mu m has been achieved. These are the first semiconductor lasers to opera te at 300K and above in this wavelength region.