Study Of Precision Measurement Technology Based On Ultrafast Laser Pump-probe Interferometry

Recently, with gradually developing of ultrafast laser technology, ultrafast laserpump-probe technology, as a time-resolved technology in ultrafast dynamics fields,had become one of research highlights in the world and was applied in testing anddiagnosing of many ultrafast processes. So it was significant to investigate how toprecisely control the relative time delay between pump light and probe light.In this paper, the pump-probe technology for optical precise measurement wasinvestigated in both theoretically and experimentally. Ultrafast laser pump-probeinterferometric system was constructed based on basic theories of ultrafast laserpump-probe technology and optical interferometry. After a series of experiments,expected results were acquired and the effectiveness of the ultrafast laser pump-probeinterferometric system was verified. Main achievements in this paper were listed asfollows:1. Optical interferometry was introduced into pump-probe technology. Ultrafastlaser pump-probe interferometric system was established with Ti: sapphirefemtosecond laser as light source and its resolution was in sub-femtosecond order.Experimental facilities, controlling programs and zero calibration were all achievedfor the system, which created conditions for following researches in optical precisemeasurements.2. With the assistance of theory of optical autocorrelation, femtosecond laserpulse width was measured by ultrafast laser pump-probe interferometric system. Bythe establishment of first-order autocorrelation function, the pulse width offemtosecond laser light source in the system was measured as34.98fs. Comparedwith the second-order autocorrelation method, the error of result was less than0.5%.3. Basic theory about the propagation of ultrafast laser pulse in transparentmedium and the relationship between phase velocity and group velocity weredescribed. According to the differences between background interferogram andsample interferogram by use of ultrafast laser pump-probe interferometric system, thephase velocity and group velocity of femtosecond laser propagated in transparentmedium were measured. The measurements were based on samples of four types andresults were listed as follows. The group velocities of femtosecond laser pulsepropagated in0o-cut YAG crystal,30o-cut YAG crystal and45o-cut YAG crystal were1.6723×108m/s,1.6745×108m/s and1.6690×108m/s. The group velocities offemtosecond laser pulse propagated in x-cut YVO4crystal and z-cut YVO4crystalwere1.4358×108m/s and1.5787×108m/s. The group velocities of femtosecondlaser pulse propagated in x-cut LN crystal and z-cut LN crystal were1.4393×108m/sand1.3951×108m/s. The group velocity and phase velocity of femtosecond laser pulse propagated in HfO2amorphous film were1.5623×108m/s and1.5348×108m/s. Compared with theoretical values, errors of results above were all in acceptablerange.