Study On The Measurement Of The Ultrashort Pulse With The Autocorrelation Method

At present, the ultrashort pulse has been a very necessary tool in chemistry, physics, plasma physics, biology and other fields, in which the ultrashort pulse is used as a short period of time probe. The parameter measurement of the ultrashort laser pulses has become an important area of research, and the related research has promoted the development of the ultrafast science. There are many pulse measurements, such as spectral phase-coherent direct electric field reconstruction, frequency-resolved optical gate, auto-correlation and so on. At present, with the advantages of stable running, easy operation, high accuracy, the autocorrelator is widely used to measure the femtosecond optical pulses.This Dissertation discusses the principles and techniques of auto-correlation method based on nonlinear effects. The design of the structure of the autocorrelator and the absorption principle of two-photon diode is introduced, thus the autocorrelation measurement methods based on two-photon absorption is given. The modified Michelson interferometer and pulse delay light path are designed and the auto-correlation analyzer device is set up. By improving the measurement circuit of the two-photon absorption diode, the problem of noise in the circuit is resolved. The aligning characteristics of the autocorrelator and the impact of the input modulation signals of the nano-translation stage to the waveform is studied. The envelope diagrams of the femtosecond laser pulse and the related curves are obtained, respectively, with a voltmeter and an oscilloscope, together with the pulse width measurement of the femtosecond laser.By the experiment, the8:1autocorrelated curves are got. For the pulsed laser of the doped titanium sapphire laser, of which the center wavelength is800nm, the measured pulse width is80fs, which is consistent with the actual value.