Enhanced optical nonlinearities in quantum well structures due to exciton localization

The third-order optical nonlinearity
\chi^{(3)}
of bound excitons can have a large value as a consequence of double multiplication of the giant oscillator strength because the
\chi^{(3)}
process involves double repetition of the excitonic transition. A proposal to use the bound exciton level in the sheet-doped quantum well structure is made to obtain a large
\chi^{(3)}
value.