Abstract

Modern photoinjectros require to use 3D profiled laser pulses for irradiation of cathode surface. The pulses make it possible to control a space-charge distribution of generated electron bunches and, in paritcular, to form electron bunches with cylindrica and 3D ellipsoidal shapes. Spatial light modulators (SLM) [1,2] and profiled volume Bragg gratings [3] can be used for control 3D intensity distribution of linearly chirped broadband infrared laser pulses. But, the widely used in photoinjectors Cs₂Te photocathodes have the highest efficiency in UV spectral range. So, the important task is to transform the profiled 3D (x,y,t) infrared pulses to visible and UV regions with high energy conversion efficiency and preserving 3D intensity distribution. It can be done with help of second, fourth and third harmonic generation (SHG, FHG, THG) processes at low group velocity mismatch of the interacted pulses. The control of the group velocities can be done by a creation of amplitude tilt or angular chirp. Here we present results of numerical simulations of SHG, FHG and noncollinear THG processes implemented for laser pulses with central wavelength 744 nm, 6 nm spectral width (FWHM) and pulse duration 15 ps (FWHM). The initial fundamental pulse has ellipsoidal 3D shape with linear grouth intensity in time.

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