Novel Quantum Cascade Devices for Long Wavelength IR Emission

There is presently a lack of efficient, compact, solid-state sources for the spectral range 1-10 THz, also known as the "terahertz gap". In fact Gunn diodes fail at such high frequencies, while from the other side, conventional semiconductor lasers are limited to the mid-infrared. Intersubband or interminiband transitions, which constitute the basis of the very successful quantum cascade (QC) lasers, possess the potential for the efficient generation of far-infrared light, although many important physical questions have to be addressed in the case of THz transition frequencies.