Luminescence spectra of a quantum-dot cascade laser

A quantum cascade laser in which the quantum wells in the active regions ar e replaced by quantum dots with their atom-like discrete energy levels is a n interesting system with which to study novel features in optical spectros copy. We study structures suitable for diagonal lasing transitions in coupl ed dots, and vertical transitions in a single dot. The luminescence spectra as a function of electron number and dot size show that for diagonal trans itions a significant amount of blueshift in the emission spectra can be ach ieved by increasing the electron population in the quantum dots as well as by decreasing the size of the dots. (C) 2001 American Institute of Physics.