  Quantum cascade lasers are recognized as propitious candidates for future
terahertz optoelectronics. Here we demonstrate several definite advantages of
quantum dot cascade structures over quantum well devices, which suffer
fundamental performance limitations owing to continuous carrier spectrum. The
discrete spectrum of quantum dots opens an opportunity to control the
non-radiative relaxation and optical loss and also provides for more
flexibility in the choice of an optical and electrical design of the laser.

Other Condensed Matter