Research On Ultrashort Pulse Propagation Based On Ray Tracing

Ultrashort pulse has many advantages,such as high peak power and very narrow pulse width,so it has been the most powerful tools for researching the interaction between laser and materials,tracing the ultrafast changes in microworld.So it is very important to study the characteristics of ultrashort pulses as the fundament of applying the ultrashort pulses,whereas temporal-spatial coupling make this procession complicated.In this essay,the changes in the characteristic parameters of ultrashort pulses were investigated,such as angular dispersion,spatial chirp,temporal chirp,pulse front tilting angle and phase,combining the ray-tracing module of ZEMAX,when ultrashort pulses pass through optical systems.The main contents are listed in the following:First of all,based on the definition of characteristic parameters of ultrashort pulses,a series of macro programs calculating characteristic parameters of ultrashort pulses were given,with combining the ray-tracing module of ZEMAX.These programs can calculate the propagation of pulses with arbitrary shapes.In addition,macro programs were applied to prism or grating system in order to investigation the changes with which characteristic parameters of ultrashort pulses change with parameters of prism or grating and the incidental conditions.The results show that characteristic parameters of ultrashort pulses increase with the increase of the dispersion of prism materials as well as the incident angle.Meanwhile,except the pulse front tilting angle,characteristic parameters of ultrashort pulses increase with the decrease of grating period,and they decrease with the increase of the incident angle.For the pulse front angle,its tendency is reverse to other characteristic parameters of ultrashort pulses.Thirdly,using macro programs the compressor consisted of four prisms was designed.Also,the changes of the second dispersion with parameters of optical system and glasses were investigated.The results show that low dispersion glass isgood at reduce the second dispersion of the compressor,so the distortion of ultrashort pulse can be reduced.Finally,according to the restrictions in pulse front tilting and temporal-spatial chirp and employing the macro programs,a broad band frequency doubling system was designed.The second harmonic pulses produced by the system had no pulse front tilting and temporal-spatial chirp.