Characteristis Of Femtosecond Laser Pulse By Using Technology Of Self-Diffraction

In recent years, the application of lasers producing femtosecond duration pulse has been extended, due to the development of laser module and technology of mode-locked. It promotes the progress of the nonlinear optics, untrafast reaction kinetics, and microbe detection. Thus it lets people understand the untrafast process in untrashort time adequately. Along with the development of femtosecond laser system, people attach important to the measurement of femtosecond pulse more and more.Precise knowledge of the pulse properties is necessary for verifying theoretical models of pulse creation. In experiments using these pulses, it is always important to know at least the pulse length in order to determine the temporal resolution of a given experiment. Moreover, in many experiments that studies of molecular vibrations additional details of the pulse's structure play an important role in determining the outcome of the experiment. Thus the convenient, intuitionistic, speediness measurements of untralshort pulse have a direction effect for experiments. At present, there are many measurement of the characteristic of pulse, for example Frequency-resolved optical gating (FROG), measured by streaking camera, and two photon fluorescence. We introduce the measurement of self-diffraction from FROG. Two beam of laser input on the surface of nonlinear optical medium and their converging point is on the front surface of medium. When the two beam of laser satisfy spatial overlap and temporal overlap, there is a transient grating on the surface of medium. Then, that transient grating is diffracting one of two beams of laser forms the signal of self-diffraction. Along with transferring the area of temporal overlap, the intensity of the signal is transferring. We make use of this point to measure pulse width and the other characteristic of pulse. Compare with other method, the advantage of self-diffraction is simpleness, detected easily and that its range of appliance is abroad.In our experiment, we measure the width of femtosecond pulse and coherent time. And we use the method of SHG to measure the same laser system for the sake of the result of self-diffraction is right. The result between two measurements is consistent in the error. Accordingly, we prove that the self-diffraction in FROG is feasible. Besides, we used a new algorithm instead of conventional generalized projections. And it achieves our purpose that measures untralshort pulse fleetly.