Second-order optical susceptibility of biased quantum wells in the interband regime

The authors develop a theory within the effective-mass approxn. of the 2nd-order susceptibility of a quantum well subject to an applied elec. field. Close to the midgap of the structure it is possible within that approxn. to reduce the normally derived triple sums over subbands to a simple sum over all the optically allowed transitions. In realistic structures, higher-energy transitions play a strong role for quant. results. This strong influence of the higher-energy transitions on the 2nd-order susceptibility has the consequence that it is not generally possible to define a quantum-well susceptibility independent of the structure in which the well is inserted. Numerical results indicate that the quantum wells should not lead to spectacular enhancements of the 2nd-harmonic-generation susceptibility. [on SciFinder (R)]