Measurement And Analysis Of Laser Pulse

The ultrashort pulse has become an important research tool in chemistry, biology, physics, plasma physics and other fields, in which the ultrashort pulse is used as a very short period of time probe. More and more studies have shown that analysis of the optical pulse fine structure have been the key in many researches. In this thesis, we study measuring the long-pulse fine structure in the time domain. The main research results are listed below.There are a number of pulse measurements, such as auto-correlation, frequency-resolved optical gate, spectral phase-coherent direct electric field reconstruction and so on. The auto-correlation can't measure the pulse fine structure in the time domain, although the following two methods can measure pulse intensity and phase characteristics and can accurately measure ultrashort pulse shape. Above two methods of experimental operation are too complicated with difficult process operation.A method of measuring the long-pulse fine structure in the time domain based on synchronized ultrashort pulse is proposed, compared to current measurements that is simple, convenient and high precision measurement, and the synchronized ultrashort pulse is used as the probe signal. Cross-correlation signal is then generated in the nonlinear crystal by nonlinear sum-frequency interaction between the probe pulse and the long pulse. Not only it may measure the long-pulse width, but also can measure the long-pulse fine structure in the time domain. The fine structure of a picosecond Nd:YLF laser pulse is obtained by a synchronized femtosecond pulse experimentally. The effect of group velocity mismatch to measurement results is also discussed finally, and experimental results show the feasibility and correctness. We also built a experiment with the autocorrelator FR-103XL, and measure the 800nm femtosecond pulse width that generated from Nd:YAG LASER. The measurement issued is 115.6fs, which is consistent with the actual width.