Electromagnetic Waves And Photo-plasma Interaction And Its Application Research

Plasma is made up of free electrons and plus ions with same electricity quantity, and neutral particle. The free electrons and plus ions will be forced by electric field while electromagnetic wave transmitting at plasma plate, then the transmission characteristic of the incident wave will be changed.Photo-induced plasma is that forming a plasma-sphere at a semiconductor plate by laser illumination. The transmission characteristic of optical-wave and electromagnetic wave will be changed while the optic-parameter and electric-parameter of the semiconductor altered by the photo-induced plasma.Optical-controlled micro-wave devices based on photo-induced plasma have been of recent interests for home and abroad researchers, because photo-induced plasma responses fast, and can be rebuilt. There have been lots of reports about products such as fast photoconductive semiconductor Switches, microwave phase shifter, microwave pad, millimeter-wave scanning antenna etc.First, the mechanics for forming photo-induced plasma are introduced in this thesis, the distribution model of transverse and lengthwise direction are established, also the expression of optical induced carrier distribution while semiconductor wafer illuminated by steady laser is deduced. The influence effects of material and laser parameters on carrier distribution are discussed.Secondary, with the dielectric constant model of photo induced plasma under the effects of electromagnetic wave, the relationships between optical induced carrier density and electromagnetic wave transmission characteristic such as reflection, transmission, attenuation, phase shift, are analyzed. At the same time, the transmission characteristic of different frequency wave at photo-induced plasma with the same carrier density is analyzed.At last, the photo-induced plasma applications at electromagnetic controlling are induced, especially the controlling of THz wave and optical controlled Fresnel plate scanning antenna. The influence factors on gain effects of the optical controlling Fresnel plate scanner are analyzed, the controlling of the laser power on the transmissivity of 94GHz is calculated, and the laser illumination models for 94GHz millimeter wave are designed. The gain effects of optical controlled Fresnel scanning antenna and metal antenna are measured, the gain of plasma antenna is about 4dB but the calculation result is 6.5dB, the gain of metal antenna is 18dB and the calculation result is 21.1dB. The reasons that the experiment result was not the same with the calculation and the plasma gain was not good as the metal are analyzed; also, the suggestions for improving experiments results are extracted.