Research Of Stretching Of Femtosecond Laser Pulse

Femtosecond laser micro-processing has great scientific value and important use in many fields. For the same material, the quality of femtosecond laser micro-processing is much better than that of nanosecond laser micro-processing. It possesses no damnification of material and characteristic of high quality of processing, it's the developmental direction of laser exact processing in 21 century.For gain high energy and high peak power of light pulse,we need magnify the femtosecond laser pulse.But there are some disadvantageous infection in the course of femtosecond laser magnification, now we all adopt chirped pulse amplification or light parameter chirped pulse amplification. at present,the pulse stretch and compress switch technology is the successful key of the technology.Now the research of compressor has go to maturation,in recently years,the research is concentrated on the stretcher. In the background,the thesis makes an theoretical and experimental deep research on the two-double stretcher.We unfold the two-double stretcher, introduced ray traced method to calculate the second order dispersion of the stretcher,and on this base we analyse the infection of the parameter of the stretcher to the second order dispersion viz the multiple of the stretcher.This offer the gist to our experimental modulation.In the stretcher, it can not only introduce the second order dispersion,but can introduce the third and high order dispersion.By analyzing,we know the high order dispersion has little infection to the width of the pulse,but when the pulse is very narrow,it can make the pulse aberration and distortion.but it can be compensated in the latter compressor.By Fourier transform,we make an particular calculation on the formula of the multiple of the stretcher,and gain an integrity calculate formula.Stretcher and compressor are conjugated, so the positive and negative dispersion can be compensated.We notice that in the stretcher,when the light incidence on the concave mirror,it will bring the spheral aberration and the spheral aberration will arouse the negative dispersion.Considering the multiple of the stretcher, we expect the negative dispersion as less as it can, thereby the total dispersion of the stretcher will be greater.In the design of the CPA system,we first put forword that we can calculate the positive dispersion aroused by the material in the amplifier in advance.When we know the surging times of the pulse in the amplifier,we can adjust the parameter in the strecher,make the positive-negative dispersion counteracted, and it can reach the optimal compensation.Considering the above factor,we design the stretcher and require the multiple of the stretcher is as great and the bulk is as small as it can ,the structure is tightened,vail to adjust...