Electron intersubband normal incidence absorption in InGaAs/GaAs quantum wells*

Abstract

Normal incidence electron intersubband transition in InGaAs/GaAs square quantum wells has been observed. With the incident light polarized (x axis) perpendicular to the growth direction (z axis) of the quantum well, a distinct absorption peak was observed. The absorption peak occurs at a different frequency from the peak induced by a mixed yz-polarized light. The latter has a smaller peak strength and is shifted at a lower frequency in the absorption spectrum, and the shift can be interpreted in part as a result of the depolarization effect. The mechanism responsible for the observation of the normal incidence absorption is discussed.