Multi-Pass Optical Parametric Chirped Pulse Regenerative Amplification Technology

Considering the huge potential application of ultra-short and ultra-intensity laser pulses in physics,biology and chemical domain,the technology of pulse energy amplification has been becoming one of the researching focuses.The Optical Chipped Pulse Parametrical Amplification(OPCPA) technology is quickly adopted as a main way to amplify pulse energy for its high single-pass gain efficiency,broad bandwidth, low pre-pulse ratio,high beam quality and so on..This thesis mainly focuses on the research of OPA system pumped by long pulse duration sources,aiming at resolving the problem of low pumping efficiency,gain saturation and reversing pumping.The thesis provides a new short pulse amplification method based on the ring cavities.The ring cavity well provides the necessity to build an OPA system with high gain and high conversion efficiency.Because of the parametrical gain and the conversional efficiency is not only related to the pump intensity,the length of the nonlinear crystal,but also related to the synchronization between the pump and seed pulse.Under the condition of the ring cavity,on the one hand,this structure compresses the pump in order to improve its intensity;on the other hand,it guarantees the seed pulse synchronizes with the pump at different time windows,which makes the multi-pass OPA become true.The research work of this thesis can be summarized as follows:1.After having a deep understanding of the principle of optical parametrical amplification,we analyzed the influence of the phase-matching condition and the parametrical bandwidth on the output pulses.Numerical simulation shows that the largest parametric bandwidth can be obtained only when the non-collinear OPA system operates at degeneracy point.2.The pre-requisite of a high efficient OPA is phase-matching.This thesis presents a theoretical analysis of the basic principle of the phase-matching.Using numerical method,the phase-matching angles of some most common nonlinear crystals have been calculated under both collinear and non-collinear conditions.3.Concerning the difference of the pulse duration between the seed and pump pulse,a new multi-pass OPA method based on ring cavities has been proposed.By adjusting the angle between the two cavities,the widest parametric bandwidth can be achieved.4.For the problem of gain saturation,based on the superposition principle of light,a new method based on ring cavity for amplifying pump pulse intensity has been proposed.Theoretical study and details of design of cavity are also been discussed.Numerical simulation of this method manifests that this method can largely improve the parametric gain,as much as 2.2 times.Furthermore the crystal length needed for certain gain is largely reduced.5.A new laser pulse energy amplification method,called multi-pass pump intensity intensified optical parametric chirped pulse amplification,has been proposed. Numerical experiment shows that this method can greatly improve the conversion efficiency to 30%in the OPA system pumped by Nd:YAG laser.