Transmission Properties Of Laser Pulses In Plasma Gratings

This thesis is devoted to studying two issues using the laser transmission theory andone-dimensional particle-in-cell simulation methods. First, Transmission properties oflaser pulse in plasma grating are studied with one-dimensional particle-in-cell simulation.Particle-in-cell simulations show effects of the pulse speed reduction, pulse stretching aswell as transmitting and localized solitonlike structure in plasma grating. Then, we studythe splitting of ultrashort laser pulses propagating in non-uniform plasmas and thegeneration of solitonlike structures.Transmission properties of laser pulse in plasma grating are studied withone-dimensional particle-in-cell simulation. The results show that the initial plasma density,laser intensity and frequency influence laser transmission in plasma grating together.Particle-in-cell simulations show effects of the pulse speed reduction, pulse stretching aswell as transmitting and localized solitonlike structure in plasma grating. Plasma gratingexhibits a wide photonic band-gap, near which the obvious forbidden band reflectionappears. When improving the laser intensity, forbidden band towards lower frequency. Incertain frequencies, plasma gratings of low density can produce transmitting solitonlikestructure. When increasing the light intensity, the electromagnetic field tends to becaptured in grating easily, forming localized solitonlike structure.Transmission properties of ultrashort laser pulse in inhomogeneous plasma grating arestudied with one-dimensional particle-in-cell simulation. The results show that the laserintensity and Plasma density gradient influence laser transmission in non-uniform plasmagrating together. When improving the laser intensity, the density where laser pulses arereflected increases and the group velocities of soliton decrease. While improving theplasma density gradient, the density where laser pulses are reflected decreases and thegroup velocities of soliton decrease. The total reflection happen when the soliton pulsesspread to plasma area of high density gradient. Due to the energy losses of soliton pulse inthe spread process, the low frequency pulse is captured in plasma, forming localized solitonlike structure, and the high-frequency soliton pulse is continue to spread, then thepulse split..The thesis is organized as follows. The first chapter gives a brief introduction ofdeveloping process laser technique, the interaction of laser pulse with plasma, inertialconfinement fusion. In the second chapter, we show the theoretical model of the deepdensity modulation of plasma, the phase reflection and coupled mode theory. What’smore, we introduce the pulse stretching and chirped-pulse compression and fastcompression of Bragg grating. Then, in the third chapter, transmission properties of laserpulses in plasma gratings are explored. Chapter four presents the splitting of ultrashortlaser pulses propagating in non-uniform plasmas and the generation of soliton-likestructures are studied with one-dimensional particle-in-cell simulation. As the conclusion,in the last chapter, we briefly summarize the total subjects and give an expectation for thefuture work.