Abstract

At present, application of the technique for chirped pulses amplification made possible to create table top terrawatt solid-state lasers.¹ The basic scheme of such lasers includes the following stages: generation of short pulses with low energy; expansion and chirping; amplification up to considerable energy; and compression to initial durations with reaching of high powers. Initially, pulse expantion was performed in fiber optical guides by means of nonlinear phase modulation. Later, other methods with application of diffractive gratings appeared. They permitted to advance the shorter pulses (< 0.1 ps) by application of spectral broad-band crystals, such as TiAl₂O₃ or LiSAF, and the pulses with the highest energies (duration 1 ps) by application of Nd-glasses. We investigated a scheme² with additional compression of picosecond pulses of considerable energy by means of nonlinear phase modulation down to subpicosecond durations which may be used for main applications.³ Variation of the compression degree and of pulses contrast was studied in dependence on their shape, parameters of the medium, type of applied compressor, inhomogeneity of the pulse phase along the beam profile and limitations by competing nonlinear processes, such as: stimulated Raman scattering, filamentation, optical breakdown of phase modulators and diffractive gratings.

© 1996 IEEE