Solid-state laser induced microwave effects

摘要

Intense laser radiation that is intensity modulated at microwave frequencies produces microwave radiation from a variety of solid-state materials that is band limited by the bandwidth of the laser modulation. An experimental investigation is summarized that provides data on the wavelength, laser intensity, laser modulation frequency, angular distribution, and, in some cases, electric field dependence on the microwave radiation that is produced. When the wavelength of the laser is sufficiently short such that electrons are promoted from the valence to the conduction band, it is clear that the radiation results from the dipole layer radiation resulting from these electrons accelerated in the electric field produced by band bending at the surface or in the PN junction of devices. There appear to be other mechanisms operative in materials such as Ge and ponderomotive forces seem likely. Also poorly understood at this time is the radiation from materials such as ZnS which has a cubic dependence on the incident laser intensity. It is suspected that nonlinear optical effects may be responsible. Although this article only presents experimental results for modulated Q-switched Nd:yttrium-aluminum-garnet laser systems, the authors have obtained entirely consistent results using other laser systems and these results are not presented for the sake of brevity. The production of laser induced microwave effects appears to be a relatively ubiquitous effect in many materials that may provide a useful solid-state diagnostic tool (with improved understanding) or probe of a material's electromagnetic properties. (C) 2002 American Institute of Physics. References: 35