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Research On Application Problems Of Object Image Grating Self-tiling In Ultra-short Ultra-high Lasers

Posted on:2016-02-22Degree:DoctorType:Dissertation
Country:ChinaCandidate:C Y LiFull Text:PDF
GTID:1108330482467716Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Recently, the development of ultrashort ultrahigh petawatt-class (1 petawatt equals to 1015W) lasers using the chirped pulse amplification technique is seriously limited by the limit-size of available gratings. In this condition, grating tiling technique has to be used to meet the requirement. Unfortunately, the high tiling difficulty and low optical performance of the traditional grating tiling make against the constructions of petawatt lasers. Thereby, we proposed a new technique named as object-image-grating self-tiling, which relieves the above two problems a lot. At present, the object-image-grating self-tiling is a good solution for the problem of limit-grating-size within a petawatt-class laser. Especially, it is much more suitable for a femtosecond petawatt laser. The reason is that there is no piston error within an object-image-grating self-tiling grating, and then the duration jitter of compression pulses will be avoided conveniently. For the urgent requirements, this paper will carry out the pre-research of the object-image-grating self-tiling applied in petawatt laser facilities. My works will focus on some potential application problems, corresponding solutions, small-scaled demonstration experiments, application designs, and some related techniques. Finally, I hope it can be used to help meet the requirement of large-sized-gratings within petawatt laser facilties and to support extremely ultra-short ultra-high lasers.The details of my works are summarized as follows:1) The problems of tiling accuracy, tiling stability and tiling benchmark monitoring within the object image grating self-tiling are solved theoretically and experimentally. A closed-loop automatic controlling system is developed, and then a near-ideal tiling condition is achieved and maintained automatically.a) A theory model for describing the electric field of a beam diffracted from tiling gratings is set up. The adjustment accuracy requirement of the traditional grating tiling and the object-image-grating self-tiling are analyzed. A contrast experiment on stability of two grating tiling are carried out, and results show that the object-image-grating self-tiling is more stable. This result is explained theoretically using a statistical method. A closed-loop automatic control system is developed, and the fast establishment and long-term maintaining of the near-ideal tiling condition are achieved.b) The object-grating is the tiling benchmark for an object-image-grating self-tiling, a method for precision online monitoring three-dimensional angular drifts of the object-grating is proposed. Monitoring objects include all dimensional angular drifts of a grating. Monitoring contents contain direction and amount. Monitoring accuracy of tilt, tip, and rot are around ±0.5μrad, ±0.5μrad, and ±1.67μrad.2) The problems of zero-order diffraction beam and related dispersion correction within the object image grating self-tiling compressor are solved. Problems of spectral modulation and pulse overlap are simulated theoretically.a) To avoid damage of amplifiers caused by the zero-order diffraction beam, the incident beam of an object-image-grating self-tiling compressor is slightly tilted to the grating groove direction with an out-of-plane tilt angle. The out-of-plane tilt angle will lead to a dispersion distortion. A third-order dispersion compensation is proposed for the Nd:glass picosecond petawatt system by inserting a length-optimized silica fiber and adjusting the grating distance within the compressor. In Ti:sapphire femtosecond petawatt lasers, the out-of-plane tilt angle can be used to compensate the material dispersion.b) The spectrum modulation and the pulse overlap of the object-image-grating self-tiling compressor within Ti:sapphire and Nd:glass lasers are simulated, respectively. The results show that the spectrum modulation will not distort the compression pulse obviously, and the pulse overlap will not damage compression gratings.3) The first experimental demonstration of the object image grating self-tiling in a CPA system is finished. A compressor design based on the object image grating self-tiling is proposed for ten-petawatt laser facilities. A method to measure the residual angular chirp of laser beams after compressors is proposed, as well.a) The temporal and spatial performance of chirped-pulse compression and beam focusing of an object-image-grating self-tiling grating compressor is demonstrated in a small-scaled optical parametric chirped-pulse amplification laser. A 1.5 times Fourier-transform-limit pulse duration, and a 1.9 times diffraction-limit focal spot are obtained, synchronously. A contrast experiment using a non-tiled grating compressor with equal-sized individual gratings is carried out, and the temporal and spatial results of two experiments are almost the same.b) An object-image-grating self-tiling compressor design for a ten-petawatt laser is proposed. The design is based on the available commercial gratings, and the problem of limit-grating-size is solved. A divided compressor structure (include a 1st and a 2nd compressor) is used to reduce the sizes of the compressor and the vacuum chamber. A dispersion corrector is introduced to improve the result and the difficulty of the dispersion management, which can also be used to adjust the duration of the final pulse conveniently.c) In order to guarantee the performance of a grating tiling compressor, a method to precisely measure residual angular chirp of CPA lasers is proposed. The amount of residual angular chirp is obtained by analyzing the far-field focal spot of the final pulse. For a 100mm beam aperture Ti:sapphire laser, the theoretical accuracy will be around 0.1μrad/nm. Besides, this method supports single-shot and online measurements.
Keywords/Search Tags:Petawatt laser, chirped pulse amplification, grating compressor, grating tiling, object image grating self-tiling
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