| The ultra-fast and ultra-intense laser have a wide range of applications in research fields such as strong-field physics,laser accelerator,time-resolved spectroscopy,micro-processing and so on.Chirped pulse amplification(CPA)technology is the main way to produce ultra-fast and ultra-intense laser.In the CPA system,dispersion management runs through the entire system,and good dispersion compensation plays a very important role,and even determines the final output indicators of the CPA system.In this paper,theoretical and experimental researches were carried out on dispersion compensation in the CPA system.The main research contents and innovative achievements of this paper are as follows:1.The influence of dispersion on ultra-fast laser was analyzed theoretically.The analysis and calculation of dispersion for common components in CPA system were given,including the dispersion introduced by transmission element,as well as the basic principle and the calculation of the dispersion of classic Martinez stretcher,(?)ffner stretcher and grating pair compressor.To compensate the dispersion of the CPA system accurately,the design of the matching scheme of the stretcher and the compressor was introduced.Taking the grating pair compressor as an example,the expression of structural parameters of the grating pair compressor was obtained under the condition that the group delay dispersion and the thirdorder dispersion introduced in the stretcher and amplifier were known.2.A concentric stretcher based on a transmission grating was designed and built.The dispersion characteristics of the stretcher were analyzed theoretically and applied to the k Hz Ti:Sapphire regenerative amplifier.The seed light output by the Ti: Sapphire oscillator was stretched to hundreds picosecond level by concentric stretcher and then was injected into the Ti:Sapphire amplifier for energy amplification,and reflective grating pair was used to compensate the dispersion at last.The structural parameters of the grating pair compressor were calculated by expression of structural parameters.Ultra-fast laser pulse was obtained with a pulse width of 47.5 fs and a single pulse energy of 1.5 m J.3.By calculation,the grism pair can provide negative group delay dispersion and third-order dispersion at the same time,while the group delay dispersion and third-order dispersion introduced by most materials in the near infrared are both positive.Therefore,a bulk material-grism pair scheme was designed in the Ti:Sapphire amplifier.An multi-pass cell bulk material stretcher was built and the seed light was stretched to 15.5 ps after H-ZF52 A with a total optical length of 500 mm.A 1250 line/mm transmission grating and a fused quartz prism with a vertex angle of 57.3° were used in the grism.The gratings were arranged in Littrow angle of 1250 line/mm to get a best diffraction efficiency.After adjusting the spacing between the dispersive prism and the grating and the amount of prism insertion,the ultra-fast laser pulse with the pulse width of 50.6 fs was obtained finally.4.The 10 Hz TW level Ti:Sapphire amplification system was aligned.The pulse width of seed light was stretched to 250 ps by Martinez stretcher.Single pulse energy was amplified to 12.2 m J after the front stage regenerative amplifier,and the main amplifier was a 6-pass Bowtie structure multi-pass amplifier in which single pulse energy was amplified to 81.4 m J.A single pulse energy of 58.2 m J and a pulse width of 43.7 fs were obtained after reflective grating pair compression,corresponding to a peak power of 1.3 TW. |
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