Direct measurement of dispersive nonlinearities in GaAs

Abstract
Nonlinear refractive index changes in 299 Å multiple quantum well GaAs were obtained directly by measuring Fabry–Perot transmission peak shifts. These changes crosscheck those obtained by Kramers–Kronig transformations of the nonlinear absorption under identical pumping conditions. High intensities saturate the exciton, so that nonlinear refractive index changes are dominated by nonresonant contributions. Thermal refractive index changes were also measured directly.