The Characteristics Of Doubling Frequency Of Ultrashort Pulses With Spectral Angular Dispersion Method

Ultra-short pulses with the characteristics of narrow time width and high peakpower have been widely used in many fields, exemplified by “ultra-fast process” inthe time resolution, laser etching in the photo etching and laser catalytic in thechemistry etc. Currently, because of relatively less kind of ultra-short pulsefrequency band generated by solid laser, optical frequency conversion technologyhas become a significant approach to obtain new pulse frequency, the most basic wayof which is second harmonic generation (SHG). Due to the wide frequency range ofultra-short pulse, SHG of ultra-short pulse is different from monochromatic laser, notonly need take phase matching into account, but also must compensate the dispersioncaused by nonlinear medium and eliminate the pulse distortion during the SHGprocess.Based on the optical frequency conversion technology, this paper has adoptednumerical simulation and experimental confirmation to analyze broadband SHG ofultra-short pulse. At the part of numerical simulation, firstly we model the opticalsystem in ZEMAX, build merit function to optimize the optical system so as toobtain the parameters of the optical system. Using Ray-pulse matrix method toevaluate the propagation of ultra-short pulse in angular dispersion SHG devices, wededuce wave front tilt pulse electric field and write numerical simulation program ofwave front tilt pulse SHG in BBO crystal by Runge-kutta method, and then achieveoutput field of harmonic and fundamental wave with the different tilt and powerwhen ultra-short pulse focus on the different positions. Moreover in ultra-short pulseSHG experiments, according to theoretical path, ultra-short pulse angular dispersionand direct SHG experimental devices are set up. The changes of the conversionefficiency have been explored. Results show that the numerical simulation results are in good agreement with the experimental. This paper determinate that numericalsimulation and experimental confirmation in ultra-short pulse broadband SHG indetail, provide a certain basis for subsequent study.