Nonlinear and bistable reflection minima at lambda = 10.6 microm in an attenuated total reflection configuration with a highly doped n-GaAs film.
n-GaAs can be so highly doped that its plasma frequency is larger than the associated frequency of a CO2 laser emission line, leading to a negative real part of the dielectric permittivity. We studied linear and nonlinear reflection properties of structures composed of such thin highly doped n-GaAs film in an attenuated total reflection (ATR) configuration. We show that deep reflection minima coincide with the excitation of Brewster-type modes of the multilayer structure. These minima feature strong nonlinear and bistable behavior and are sensitive to geometrical and material parameters. The proposed ATR configuration can be used to determine doping concentrations with an accuracy of better than 1 partper thousand and different deformation potentials of the higher-conduction bands in n-GaAs.