Shaping picosecond ellipsoidal laser pulses with periodic intensity modulation for electron photoinjectors.

A method for shaping periodic intensity distributions of strongly chirped picosecond laser pulses in the infrared range by periodic phase modulation of the spectrum is proposed. The dependence of the time modulation period and depth on the parameters of periodic phase modulation of the spectrum is analyzed by analytical and numerical methods. It is demonstrated that the intensity distribution structure obtained at second- and fourth-harmonic generation can be retained by introducing an angular chirp.

Retaining 3D shape of picosecond laser pulses during optical harmonics generation.

Collinear and noncollinear sum-frequency generation of broadband laser pulses with angular and frequency chirp is considered. The conditions of minimal distortions of 3D ellipsoidal intensity distribution of triangular chirped femtosecond pulses during generation of the second, third, and fourth harmonics of a Ti-Sa laser in LBO, BBO, and KBBF crystals are found using numerical methods. The efficiency of conversion from the fundamental to the fourth harmonic (45%) is higher than to the third harmonic (20%), and the distortions of intensity distribution are less.

Shaping of cylindrical and 3D ellipsoidal beams for electron photoinjector laser drivers.

With the use of spatial light modulators it became possible to implement in experiments the method of controlling the space-time intensity distribution of femtosecond laser pulses stretched to picosecond duration. Cylindrical and quasi-ellipsoidal intensity distributions were obtained and characterized by means of a 2D spectrograph and a cross-correlator.

Disk Yb:KGW amplifier of profiled pulses of laser driver for electron photoinjector.

We investigated a diode-pumped multipass disk Yb:KGW amplifier intended for amplifying a train of 3D ellipsoidal pulses of a laser driver for a photocathode of a linear electron accelerator. The multipass amplification geometry permitted increasing the energy of broadband (about 10 nm) pulses with a repetition rate of 1 MHz from 0.12 µJ to 39 µJ, despite large losses (two orders of magnitude) introduced by a beam shaper of 3D ellipsoidal beam.