Device Physics of Intersubband Lasers

Abstract

Solid state microwave oscillators generate electromagnetic radiation by accelerating electric charge and can operate up to frequencies of around 150 GHz (2 mm). Solid state optical sources of electromagnetic radiation work on a fundamentally different principle, with photons generated as a result of electron transitions between discrete states. Devices based on cross-bandgap electron-hole recombination are available typically down to frequencies of around 150 THz (2–3 µm). Recent work on unipolar solid state optical sources has extended this down to around 70 THz (13 µm). The purpose of this work is to give an outline of the physics of these intersubband devices which generate photons via electron transitions between excited conduction band states localised in quantum wells.