Non-Drude-Like Behavior of the Photoinduced Dielectric Permittivity of GaAs and Si in the Gigahertz Frequency Range.

The non-Drude-like behavior of the real part of the photoinduced permittivity Re ε_P of GaAs and Si samples in the gigahertz range is detected by direct cavity measurements under conditions of fiber-optic irradiation at a wavelength of λ = 0.97 microns with changing power P in the range of 0–1 W. It is shown that, in accordance with the hypothesis of the exciton mechanism of photoinduced microwave dielectric permittivity, Re ε_P increases with increasing P (approaching saturation above P = 200 mW) instead of decreasing within the framework of free-charge carriers according to Drude. The generality of the behavior of the real parts of the photoinduced permittivity observed in semiconductors of different types (direct-gap GaAs and indirect-gap Si) in different electrodynamic systems (waveguides, cavities, metastructures) testifying to the universality of the exciton mechanism is demonstrated. Optically controlled metastructures in the GHz band containing resonant electrically conductive elements filled with GaAs and Si samples are proposed for the first time: a metastructure based on linear dipoles and a half-wave electric dipole based on a multipass spiral. The gigahertz responses of the metastructures and transformation of the responses associated with changes in the dielectric permittivity of Si and GaAs during photoexcitation are measured for the first time. Based on the hypothesis put forward about the effect of excitons on photoexcitation, the observed saturation effect of gigahertz photoinduced permittivity is discussed. [ABSTRACT FROM AUTHOR]