The Research Of Ultrafast Imaging System Based On Femtosecond Ultrashort Laser Pulse

Since the birth of laser,laser pulse is becoming more and more short.Now,femtosecond ultra-short pulse laser technique is already very mature.Based on the various characteristics of femtosecond lasers,in industrial,medical and scientific research fields,there are a wide range of applications.Femtosecond ultra-short pulse laser has a very high time resolution,and has important application in ultrafast diagnoses.In 2004,a sequential timed all-optical mapping imaging system has been put forward,it through the modulation of femtosecond ultra-short pulse laser,as a lighting source.Through the pulse stretching system stretching the femtosecond laser pulses,and through the pulse shaping system make the input pulse into six daughter pulses,then lighting the sample,and then,through the pulse spatial mapping system,make the six daughter separate in the space.And then use the CCD to acquire six pictures through the imaging system.This ultrafast detect method has very high time resolution.In this letter,we studying this method,analysis and research in the theory and experiment.The main work in this paper includes some aspects as follows.(1)This paper is mainly study the modulation of the femtosecond ultra-short laser,to get the pulse of what we want,and building imaging system to acquisition process of ultrafast event.Through the pulse stretching system to stretch the input pulse of 25 fs into 27 ps.(2)we set up a pulse shaping system make the pulse which through the pulse stretcher,into six daughter pulse which pulse width is 900 fs,frame interval is 4.5ps.(3)we set up a pulse spatial mapping system,through the beam lifter make the six daughter pulse to separate in the space.(4)In this thesis,we designed a static imaging experiment,to shooting three scale line on the transparent reticle,and use two beam lifter to separate two of the six daughter pulse,and in one exposure acquired two pictures of the scale line,verified the feasibility of the whole imaging system.(5)In this thesis,we also a dynamic imaging experiment,to shooting the plasma in a laserdriven ionize the air molecular,first we debug the imaging light-path and acquire the six daughter pulse use the CCD detector in one exposure.Until now we have not catch the motion picture of the ultrafast event.So we analyzed the whole experiment,and found the problem,and make a list of what we should do next.