Photoelasticity effects in superlattices with quantum wells having a sloping bottom near the interband resonances

An analytical expression is obtained for the linear coefficients of photoelasticity in superlattices with quantum wells having a sloping bottom in the vicinity of the interband resonances. It is shown that these coefficients considerably decrease when the slope of the quantum-well bottom is induced by an electric field applied to the superlattice and remain almost unchanged if the slope is produced by the variband method. A new mechanism providing the emergence of linear photoelasticity near the interband resonances is revealed for superlattices based on piezoelectric crystals. This mechanism is associated with the modulation of the band gap of the quantum-well structure by the generated piezoelectric field. Numerical estimates demonstrate that the contribution to the linear photoelasticity in the region of the interband resonances is substantially greater than the corresponding contribution in the exciton region of the spectrum and is comparable in magnitude to the contribution made by the deformation potential.