Excitonic effects can lead to decreased intersubband oscillator strength

We study intersubband transitions of an electron in a quantum well, in the presence of a hole. When the energy of one subband of the electron approaches the top of the well, the electron-hole attraction strongly influences the electronic state. We show that these excitonic effects lead to a reduction in oscillator strength for an intersubband transition of given energy. This finding should be considered in the design of quantum well devices, such as recent devices that produce midinfrared radiation from near-infrared laser structures.