Dispersion of nonlinear optical susceptibility of GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As multiple quantum wells in the exciton region

The dispersion of ${\mathrm{\chi }}^{\mathrm{}\left(2\right)\mathrm{}}$(2ω) by the refelction of incident light from GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As multiple quantum wells at room temperature with wavelength between 8000 and 9000 Å has been measured. The nonlinear susceptibility ‖${\mathrm{\chi }}_{14}^{\mathrm{}\left(2\right)\mathrm{}}$(2ω)‖ shows two pronounced peaks at 8436 and 8490 Å. It is suggested that one peak corresponds to the light-hole-exciton absorption and the other to the heavy-hole-exciton absorption.