Use of double-grating Offner stretcher for dispersion control in petawatt level optical parametric chirped pulse amplification systems

The aberration-free characteristic endows the double-grating Offner stretcher with the advantages of good beam quality and perfect-dispersion-match with conjugated Treacy compressor, and therefore makes it an ideal pulse stretcher for optical parametric chirped pulse amplification (OPCPA) systems featuring with low material dispersion. We numerically and experimentally demonstrate the feasibility of dispersion control in OPCPA systems by the use of double-grating Offner stretcher. The numerical results indicate that near Fourier-transform limited (FTL) pulses can be realized in the double-grating Offner stretcher based petawatt (PW) level broadband OPCPA systems. Moreover, in a proof-of-principle experiment, amplified pulses with similar to 210 nm spectral bandwidth and similar to 3 ns chirped pulse duration are also compressed to near FTL pulse duration of 15.4 fs just by cooperating a double-grating Offner stretcher with a Treacy compressor. To our knowledge, it is the first time to realize near FTL compression of laser pulses with such a broadband spectrum and such a large chirped pulse duration simultaneously, while without using any extra dispersion compensation methods.