We investigated the interaction processes between high intensity femtosecond ultraviolet laser pulses and amorphous silica, leading to permanent refractive-index changes that are at the basis of advanced manufacturing for photonics devices. 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. Moreover, in a proof-of-principle experiment, amplified pulses with ∼210 nm spectral bandwidth and ∼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. 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. We numerically and experimentally demonstrate the feasibility of dispersion control in OPCPA systems by the use of double-grating Offner stretcher. 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.
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