Research On Ultrafast All-optical Framing Imaging Technology Based On Chirped Pulse

High time resolution is required in ultrafast physical processes, ultrafast chemical processes, and ultrafast biological processes, and many other areas of research. In order to break through the constraints of the mechanical rotation system and electronics system bandwidth in traditional high-speed photography technology, and to overcome the disadvantages of pump-probe method, ultrafast holographic framing camera, ultrafast hyperchromatic framing camera, sequence mapping all-optical framing camera etc., this paper presents an ultrafast all-optical framing imaging method based on discrete sampling record. This imaging method can realize all-optical framing imaging, coaxial framing imaging, more frames and coherent phase imaging. In this paper, several key technologies of the method are studied, including pulse stretch technology, pulse shaping technology, pulse measurement technology, discrete sampling and recording technology. The main contents are as follows.Through the analysis of the broadening principle and capacity of some typical pulse stretcher, the parallel grating pair is selected as the broadening scheme. Mathematical modeling and simulation analysis of the pulse stretcher system is accomplished, and the experimental device is built to verify the pulse broadening scheme.Based on the research of the basic principle of pulse shaping technology,4f pulse shaping system of reflective liquid crystal spatial light modulator is selected. Mathematical modeling and simulation analysis of the pulse shaping system is accomplished, focusing on the distortions caused by pixel gaps, the discrete step-type phase modulation and the nonlinear spectral dispersion of the liquid crystal spatial light modulator.4f pulse shaping system is set up, and the relationship between the gray level and the phase of the liquid crystal spatial light modulator is calibrated.In this study, several common methods of ultrashort pulse measurement are studied, and the frequency domain interferometry based on the window Fourier transform is proposed. By using this method, the linear chirped pulse and the complex beat signal are measured. Experimental results are compared with the results obtained from traditional frequency domain interferometry to verify the feasibility of the pulse measurement.Discrete sampling and recording system is designed, and the ray tracing of the simulation software is used to verify the feasibility. The dispersion ability of some common dispersive elements is tested, and the dispersion component matched with the recording system is selected. The recording system is used to complete the experiment of the laser spot imaging and resolution imaging, and the spatial resolution and time resolution of the system are also analyzed. The interference fringes produced by Michelson interferometer are recorded by the discrete sampling and recording system. The coherence phase imaging capability of the ultrafast all-optical framing imaging system is verified. Combined with the research results of pulse broadening and pulse shaping, the paper theoretically analyzed the technical index the system can achieve.