Generation of the Second and Fourth Harmonics with Retaining the Three-Dimensional Quasi-Ellipsoidal Distribution of the Laser Pulse Intensity for a Photoinjector

We consider the possibility of generating the second and fourth optical harmonics of laser pulses having a central wavelength of 1030 nm with retaining the three-dimensional quasi-ellipsoidal intensity distribution. The presented results of numerical simulation confirm that angular chirping allows one to retain the three-dimensional structure of the intensity distribution and enhance energy conversion. The proposed approach was tested experimentally using non-profiled laser beams. Energy conversion efficiency of 53% and 21% was achieved in the generation of the second and fourth harmonics, respectively.