Design And Implement Of Spectral Phase Interferometry For Direct Electric Reconstruction System

After the invention of ruby laser by Maiman in the 1960 s, scientists have been focusing on the improvement of lasers, from CW- laser ? Q-switched laser to picosecond and femtosecond laser based phase locked technology, the pulse duration of laser becomes more and more short while the peak power becomes more and more high, which makes it widely used both in laboratory and industry. As a basic work,it is the primary task for scientists to measure the pulse duration and phase, especially the duration and phase of ultra- fast laser such as picosecond or femtosecond laser. When it comes to the pulse duration of nanosecond laser, people could use oscilloscope to measure, but one could not use oscilloscope to measure the pulse duration of picosecond or femtosecond laser. Although streak camera could be used to measure it,it could not be widely used in laboratory because of its high price. Actually, except for the method mentioned above, scientists have already come up with three other widely used methods to measure the pulse duration and phase of pulse: Autocorrelation(AC) ? Frequency Resolved Optical Gate(FROG) ? Spectral Interferometry for Direct Electric Reconstruction(SPIDER).In this paper, we make use of the method of SPIDER. By making two frequency-shifted pulses interfere with each other, one could work out the phase of the incident pulse by applying fourier-transform and trapz or overlay method. After that, by introducing the incident spectrum of the incident pulse, one could reconstruct the pulse in the time domain and calculate the pulse duration. The main research details in this paper are :Discusses the relationships and differences between linear correlation?nonlinear correlation and spectrum interferometry, demonstrates the possibility of usage of s spectrum interferometry in the measurement of pulse duration and phase of laser pulses, presents the principle of phase cumsum and the optimization method of it.Discusses the impression of frequency-shear leave on interferometry of the frequency-shifted pulse, shows the varies the frequency-shear leaves on the interferometry spectrum in time domain by simulation, puts forward a method to select rectangular filtering or gaussian filtering function based on interferometry in time domain. Discusses the phase- matched width differences between the two different types of BBO crystal, comes to a conclusion about the parameter of the BBO crystal such as phase- matched type and thickness.Talks about the appropriate pulse duration of the stretched pulse, comes to a conclusion about the parameter of grating pairs.Discusses the possible application of method of twice-reconstruction of both pulse duration and phase in reconstruction of pulse duration and phase of ultra-fast laser, makes a conclusion about this method. Discusses the impression the different order between unwrapping and subtraction of phase contained in interferometry and frequency-shifted interferometry, making simulations and shows that the order of it does leave big impression on the reconstructed phase,but plots of cosines of consructed phases changing along frequencies are the same.Comes up with some schemes to improve SPIDER, presents other methods to diminish errors and improve efficiency of this system during the past ten years.By making use of the SPIDER-system, the paper measures both the pulse duration and phase of the femtosecond laser in laboratory. By collecting the related spectrum and dealing with the data with LABVIEW, the paper reconstructs pulse duration of 39 fs and works out the plots of relative phase changing along frequencies, the reconstructed phase is truthful while the reconstructed pulse duration is fit to the result of 37.38 fs achieved by autocorrelation.