Propagation of Guided Electromagnetic Waves in Semiconductors in a Longitudinal Magnetic Field

Abstract

The propagation of electromagnetic waves in a circular waveguide, filled over a finite distance with a longitudinally magnetized semiconducting medium, is studied both theoretically and experimentally. The existing theory of the propagation of guided electromagnetic waves in gyromagnetic media is extended by consideration of the attenuation of the wave by the medium. It follows from the theory presented that analytical expressions for the dependence of the propagation on the magnetic field can only be derived if the gyromagnetic properties of the semiconductor are sufficiently weak. It is shown that values of the concentration N, the mobility μ and the scattering time τ (and hence the effective mass m*) of the charge carriers can be found by measuring the Faraday rotation, as well as by measuring the attenuation of a plane-polarized wave due to the charge carriers in the medium. Furthermore, these two measurements are shown to provide a convenient way of determining the dielectric constant of a semiconductor in the microwave region. In order to verify the theory experiments were carried out on n-type GaAs. Both the Faraday rotation and the attenuation of the wave were measured, taking into account the influence of interferometer effects due to the finite length of the semiconducting medium. The experimental results obtained for the Faraday rotation and the attenuation were consistent with each other and were in excellent agreement with the theory. The dielectric constant εl of GaAs was found to be 12.77±0.1.