Research On Spatial Profiles And Temporal Waveforms Shaping And Spatial Temporal Coupling Of Femtosecond Laser Pulse

The great progresses in ultrafast and ultrahigh femtosecond pulse laser areproviding powerful tools for the investigations on opt-electronic interactions and novalphysical phenomena and rules under extreme conditions. But in many applications, justgeneral ultrafast and ultrahigh laser pulse can not be satisfied and particular temporalwaveforms and special spatial profiles of the laser pulses are needed. Pulse beamshaping techniques become indispensable to realize arbitrary temporal waveforms andspatial profiles, which have been one of the most important scientific researches inultrafast area. Both temporally and spatially shaped ultrafast pulse beam have beenapplied in the studies of ultrashort pulse code division multiple access communications,image processing in biomedicine, femtosecond chemistry, femtosecond physics andfemtosecond ablation and so on. The research target of this paper is to generate arbitaryspatial and temporal waveforms. According to this target theory and experimentalworks about pulse beam shaping and temporal-spatial coupling are investigated in detail.The main contents of this paper are shown as follows:1. The thesis begins with a comprehensive reviewing about the developmenthistory and updated achievenements and applied backgrounds of the femtosecond pulsebeam temporal and spatial shaping. Based on4f zero-dispersion Fourier transformshaping setup and direct wavefront phase modulating according to the Galileanasperical lenses shaping setup, temporal and spatial shaping are investigated. Dispersioncompensations for temporal and spatial shaping are investigated, which can be used forthe further design of the shaping system.2. The liquid cystal spatial light modulataor (LC-SLM) is the key opticalcomponent of the shaping setup, of which the relation between input voltage and phaseresponse is experimentally calibrated. Subsequently, the grayscale image phaseresponse is obtained, which can support the automatable control of the LC-SLM.Moreover, by analysis the measuring principle and simulation of the frequency resolvedoptical gating (FROG), the error of the FROG is studied, which is valuable forimproving femtosecond pulse checking and compensating the dispersion of temporalshaping. 3. In order to study the effect of mismatched spacing and angle on zero-dispersionfemtosecond pulse shaping temporal properties, the relation between the resolution andthe mismatched spacing of the system was analyzed in theory. And then the effect ofmismatched spacing and angle on the system efficiency and pulse temporal propertywas discussed. The experimental results indicate that lens misalignment will broadenthe pulse and the influence of the first grating is symmetrical with the influence of thesecond one. Moreover, the influence on system efficiency of angle misalignment ismore serious than spacing misalignment. If600lines per millimeter grating and lens of30centimeter focal length were used, when the angle misalignment is smaller than9°orspacing misalignment is shorter than0.5centimeters, the changing of system efficiencyand pulse width are both smaller than5%. All the results above are helpful to anin-depth study on the zero-dispersion pulse shaping system. Nested qusi-4f pulseshaping setup is proposed, which can disper the frequent components in two dimensionsthat can improve the usage of the LC-SLM.4. Based on Galilean refractive aspheric lens shaping theory, a setup usingLC-SLM is proposed and the spatial profile of the pulse beam is shaped. Dark hollowGaussian beam and super-Gaussian flattop beam are generated. Based on purepolarizing controlling and direct wavefront phase modulating, fentosecond radiallypolarized beam and vortex beam are generated, and the temporal properties are studied.5. Temporal-spatial properties of4f shaping setup and spatial chirp in first orderare investigated in detail. The relationships between spatial chirped Gaussian beamvortex beam radially polarized beam and spatial chirp parameters are obtained, whichare valuable for spatial chirp control and utilized.6. A setup for both temporal and spatial pulse shaping is proposed, based on whicharbitrary spatial profiles and typical temporal waveforms are generated. And thetemporal properties are analyzed in detail.In a word, this thesis proposes a system for both temporal and spatial shaping offemtosecond pulse beam. Temporal-spatial coupling and dispersion compensation andthe effects of the shaping setup on femtosecond pulse temporal proerties are studied.The effect of mismatched spacing and angle on4f zero-dispersion femtosecond pulseshaping is investigated and nested shaping system is proposed. All the results above areof potential value for improving the shaping system and designing the future minaturecompact and high efficiency shaping system.