Studies On Accuracy Improvement Of Ultra-short Pulse Propagation Recording

With the rapid development and gradual maturity of ultra-short pulse laser technology,ultra-short laser pulse has attracted more and more attentions and been widely applied to many fields of scientific research and life,including research of ultrafast phenomena,precision materials processing,ultra-precision surgery,optical communication and high-technology field.Ultra-short laser pulse has promoted the new development of physics,biology,material science,chemistry,information science and other fields.The observation of femtosecond light pulse propagation can prove relevant theoretical and experimental results of ultra-short pulse laser propagation,and can be conducive to the observation and research of ultrafast phenomena,the discovery,understanding and elaboration of the dynamic mechanics of ultrafast process,the expounding of high efficiency materials processing conditions,the optimal control of laser beam in laser processing,the optimal laser propagation conditions of femtosecond laser nanosurgery,and the characterization and mechanism research of optical device applied to photonic network and the high performance all-optical communication.Therefore,the observation of femtosecond light pulse propagation has important value and significance to various fields of research and application.In this thesis,we made a thorough and systematic study of the time-resolved ultrafast measurement techniques which can realize the observation and recording of ultra-short pulse laser propagation,and improved the accuracy of the ultra-short pulse propagation recording.And the main works and innovative points are as follows:1.Studies on accuracy improvement of light in flight(LIF)holography recording.The distortion of the reconstructed images of the propagating light pulse in transmission LIF holography recording was analyzed.And based on the simulation and comparison,for recording the wavefront more accurately,the optimized selection of relevant parameters was made in time direction,and a cylindrical lens was introduced to rectify the distortion partly in space direction.Defined the direction parallel to the bright straight line as the space direction,and the direction of pulse propagation along the diffuser and recording material as the time direction.As to the wavefront invariable during the propagation,we can make the conclusion that the distortion of reconstructed images decreases as θO(the angle between the illuminating light pulse and the diffuser plate)and d increases,so we should set the value of θO and d as large as possible to record more accurately in time direction.And as θR(the angle between the reference light pulse and the recording material)increases,the distortion remains fixed and the temporal resolution decreases.Furthermore,a cylindrical lens was introduced to rectify the distortion partly in space direction.Additionally,the LIF recording of the wavefront changing during propagation was simulated.2.We proposed a DMD STRIPED FISH technique.Compared with the STRIPED FISH technique,our scheme can simultaneously improve the frame rate and double the space bandwidth product(SBP)of sub-hologram on CCD.The spatially and temporally resolved intensity and phase evaluation device: full information from a single hologram(STRIPED FISH)tecnique can measure the full spatiotemporal field of an ultra-short pulse,and the setup is simple and compact.Based on STRIPED FISH,an improved single-frame full spatiotemporal field distribution measurement method is proposed.In our scheme,between diffractive optical element(DOE)and band-pass filter(BPF),and between BPF and the CCD camera,digital micromirror devices(DMD)are introduced to perfect the setup.Compared with the STRIPED FISH,our improved scheme can simultaneously improve the frame rate and maximize the utilization efficiency of the SBP of CCD.And simulation is carried out to demonstrate the process of the implementation,which confirmed the feasibility of the proposal.3.We propose a two-probe frequency-domain shearing interferometry.Compared with Frequency Domain Holography(FDH),our scheme has better accuracy and stability in some situations.According to whether or not the reference pulse propagates through the medium,frequency domain holography(FDH)can be divided into two types.FDH typeⅠ(reference pulse and probe pulse co-propagate through the medium)cannot measure accurately the ultrafast phase of the object with relatively large time duration due to the spectrometer’s resolution limits.By contrast,two-probe frequency-domain shearing interferometry and FDH typeⅡ(reference pulse doesn’t propagate through the medium)can overcome the limitation and reconstruct the phase more accurately.And compared with FDH typeⅡ,two-probe frequency-domain shearing interferometry can eliminate the extra step of measuring the phase caused by the material dispersion of the medium,and has greater accuracy and stability,especially for spatially distributed phase measurement.The experimental measurements of THz signal have proved the accuracy of the two-probe frequency-domain shearing interferometry.4.Studies on reconstruction accuracy improvement of the spectral phase interferometry for direct electric-field reconstruction(SPIDER).We propose a dispersion compensation algorithm with which the spectral phase errors of the recovered electric-field reconstructed with traditional SPIDER algorithm due to dispersion from the splitter of the Michelson interferometer(MI)can be alleviated effectually.By our dispersion compensation algorithm,the SPIDER can keep a simple configuration.Meanwhile,the dispersion compensation algorithm can improve the accuracy of the reconstructed electric-field for both dispersion-imbalanced and dispersion-balanced MI,which is confirmed by our simulations and experimental measurements of the 800 nm ultra-short pulse chains with different bandwidths.