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.

Theoretical and experimental study of laser radiation propagating in a medium with thermally induced birefringence and cubic nonlinearity.

We consider a problem of laser radiation propagating in a medium with birefringence of two types: linear birefringence independent of intensity and polarization, and intensity and polarization dependent circular birefringence caused by cubic nonlinearity. It is shown theoretically and experimentally that the efficiency of the broadly employed method of linear depolarization compensation by means of a 90° polarization rotator decreases with increasing В-integral (nonlinear phase incursion induced by cubic nonlinearity). The accuracy of polarization transformation by means of a half-wave and a quarter-wave plate also decreases if В > 1. By the example of a λ/4 plate it is shown that this parasitic effect may be suppressed considerably by choosing an optimal angle of inclination of the optical axis of the plate.

Propagation of laser radiation in a medium with thermally induced birefringence and cubic nonlinearity.

A system of differential equations describing, neglecting diffraction, the propagation of laser radiation in a medium with birefringence and cubic nonlinearity is derived. It is shown that the efficiency of depolarization compensation by means of a 90 degrees polarization rotator or a Faraday mirror decreases with increasing B-integral (nonlinear phase incursion). Comparison of the effectiveness of the considered method in the case of incident linear and circular polarization showed that for the circular polarization the optimal angle of polarization rotator is different from 90 degrees and the degree of polarization is less than for the linear one.

200 TW 45 fs laser based on optical parametric chirped pulse amplification.

200 TW peak power has been achieved experimentally using a Cr:forsterite master oscillator at 1250 nm, a stretcher, three optical parametrical amplifiers based on KD*P (DKDP) crystals providing 14.5 J energy in the chirped pulse at 910 nm central wavelength, and a vacuum compressor. The final parametrical amplifier and the compressor are described in detail. Scaling of such architecture to multipetawatt power is discussed.