<title>Observation of optically pumped intersubband emission from quantum wells</title>

Abstract

We report the first observation of optically pumped spontaneous emission from intersubband transitions by electrons in an n-type GaAs/A1GaAs coupled-quantum-well structure. Electrons were pumped from the first to fourth conduction subbands with a CW CO2 laser operating at a photon energy of 133 meV. The transition from the fourth to the third subbands occurred at an energy of 17 meV and had a full width at half-maximum of 3 meV.