Wide Spectrum Of High Diffraction Efficiency Of Metal/dielectric Film Grating Diffraction Characteristics Research

The Chirped-Pulse Amplification system (Chirped-Pulse Amplification, CPA) plays a critical role in the process of achievement of the high peak ultra-short pulses. The core component of the CPA system is the pulse compression gratings (Pulse compression grating, PCG) used for pulse broadening and compressing. The design and manufacture of high performance PCG is becoming an important and attractive research field. The MMDG (Metal and Multi-layer Dielectric Grating, MMDG) combines the high efficiency properties of dielectric and the broadband properties of metal. The optimization design and manufacture of MMDG attract amount of attentions from the high peak ultra-short pulses researchers.The main research works of this paper is as following:(1) The theoretical analysis model used for analysis of the MMDG diffraction performance is built based on RCWA. The optimization and design method for broadband and high efficiency MMDG is developed by optimizing the parameters (grating period, groove depth, residual thickness, duty cycle, incident angle) taking the bandwidth of the-1st order diffraction efficiency exceed97%as the merit function.(2)In order to assure the mechanical stability of the stack and reduce the fabrication error, we design a kind of grating based on two layers of irregular dielectric thin film(The optical thickness is not a quarter of reference wavelength). The diffraction performance won’t be influenced by the physical injury.(3) The fabrication tolerance of the parameters of the broadband MMDG is analyzed. It would be a theoretical guide to the manufacture of MMDG.The optimization and design of the broadband and high efficiency MMDG centered at1053nm and800nm used in CPA are mainly researched based on above method. The main achievements are as following:(1) The bandwidth of gratings based on Ag(LH)2or irregular structure can reach160nm centered at1053nm, and it can reach200nm for the grating based on Ag(LHT)2.(2)The bandwidth of gratings based on Ag(L1.5H)2or irregular structure can reach120nm, and it can reach135nm for the grating based on Ag(LHT)2.(3) Less thin film layers of irregular structure ensures its mechanical stability. Excellent fabrication tolerance of the high reflection mirrors and the gratings guarantee the practicability and the characteristics of the gratings. The designs of the PCG can develop the application of the CPA.