An expression is obtained for the oscillator strength of the main exciton transition, computed using a variational procedure in the approximation of an infinitely deep quantum well. It is shown that this quantity is a factor of (a<sub>B</sub>/λ)<sup>2</sup> greater than the oscillator strength in the bulk case (a<sub>B</sub> is the Bohr radius of the bulk exciton, and λ is the variational parameter), and this increases the polariton gap. The modulation effect by a sound wave of the reflectance of light at the longitudinal-exciton frequency in superlattices is considered, along with the diffraction of light at the sound wave. It is shown that these effects can be achieved in superlattices at temperatures one and a half times as great as for bulk crystals and with weaker requirements on their frequency.
© 2013 Optical Society of AmericaPDF Article