Measurement, Evaluation And Amelioration Of Lasser Beam In CPA System

As ultra-high intensity and ultra-short laser pulse has an important application in the field of sophisticated and advanced research, such as X-ray laser, lab celestial bodies physics,ICF,laser-particle accelerator, high-intensive field laser physics and so on, it has become the focus of related research. And as chirped pulse amplification (CPA) is an effective method to get the laser with ultra-high intensity and ultra-short pulse width, it draws global attention. Meanwhile, greater importance is being attached to the beam quality which reflects the spatial character of the laser.During studying for Master' s Degree, the author undertook the task of "Detectiion, Evaluation and Amelioration of Laser Beam " in the project of "5TW, 20fs CPA System" . This dissertation is the summing-up of the author' s research and experimental work. The main contents are as follows:1. Reviewed the history of the development of ultra-short laser pulse technology. Emphatically introduced the principles, makeup and latest progress of CPA technology.2. Studied the theoretical basis of measuring the beam quality factor by beginning with the M~2 matter of laser beam. Set up the algorithmic modle of fitting the Gaussian beam by means of second rank quadrature and nonlinear least square method. And designed the major parts of software in the beam quality diagnosis system which serves our CPA system.3. A method which uses basic Fourier transform and laser multimode theories, and by means of numerical integration with reasonably mathematical approximation, to design the size of the pinhole in the spatial filter of a CPA system is studied. In conclusion, the optimal diameter of the pinhole is about 6. 93 times the diffraction limit length. This result is well verified by experiment. In addition, a factor called"B" to help describe the quality of the pinhole-lens spatial filter is introduced.4. Discussed the methods of measuring the width of ultra-short laser pulse. Introduced the measuring principles of correlation method, analyzed the merits and drawbacks of several quadratic correlation techniques.