Light-induced Air Plasma Characteristics Of Study

With the development of laser technology,mankind can attain the laser pulses which are much shorter and more and more powerful. As the laser technology is full of potentiality in military and civil fields, it attracts many researchers.The transmission of the high power and short width laser pulse in the atmosphere is one of the common problems which researchers should face in the application of it. It may bring about much nonlinear effect when high power and short width laser pulse is being transmitted in the atmosphere. The air plasma will form when air is ionized and enough electrons are produced. This process will cause the loss of laser energy. At the same time the air plasma will block the energy transmission of electromagnetic wave in certain conditions. All these factors make the transmission of high power laser very difficult, and the laser can only go several Rayleigh lengths. However, mankind is supposed to transmit the high power laser pulse to a long distance in the practical use.This thesis aims at the transmission of high power laser pulse in the atmosphere, and emphasizes on the threshold of air breakdown from the aspect of numerical computation, the long distance transmission of high power laser in the atmosphere, and especially on the long distance tansmission of long pulse ultraviolet radiation from the aspect of theory and numerical computation.There are three main parts in this thesis:1. Some kinds of ionization of gas under the irradiation of high power laser are discussed; especially the multiphoton ionization, then the models of gas breakdown is introduced. The threshold of air breakdown induced by high power laser pulse is numerically computed; the relationship between the air breakdown threshold and initial electron, air pressure, and the width of laser pulse are also computed.2. The interaction of the air plasma induced by laser pulse and the electromagnetic wave is mentioned; especially the reason why the plasma absorbs electromagnetic wave. The loss of radar wave when it is crossing the air plasma is also numerically calculated.3. The transmission equation of high power laser in the atmosphere is deduced on the basis of full consideration of the nonlinear effect. And according to the equation we...