Impact of deformation potential scattering on free-carrier induced optical nonlinearities: An experimental study in GaAs

Abstract

We present results of the experimental determination of the optical nonlinearities induced by heating free electrons distributed in the multivalley conduction band of highly doped n-GaAs. We propose a very sensitive multilayer leaky waveguide structure for transverse magnetic polarized waves in order to drastically reduce the required optical intensities. We explain in depth the dependence of the optical nonlinearity on doping concentration and deformation potentials. For a doping concentration no of 7.6×1018 cm−3, we found a nonlinear refractive index value n2≈(1∓0.2)×10−6 cm2/W at λ=10.6 μm, by fitting nonlinear reflection measurements with an equivalent intervalley deformation potential value ΛLL=(1.0±0.30)×109 eV/cm.