High-energy pulse compression by use of negative phase shifts produced by the cascade chi((2)):chi((2)) nonlinearity

We report a simple optical pulse-compression technique based on quadratic n onlinear media. Negative nonlinear phase shifts are generated by phase-mism atched second-harmonic generation, and the phase-modulated pulses are then compressed by propagation through materials with normal dispersion. Millijo ule-energy pulses from a Ti:sapphire amplifier are compressed from 120 to 3 0 fs, and calculations indicate that compression ratios of >10 are realisti cally achievable by use of this approach with optimal materials. The insert ion loss of the compressor can be less than 10% of the pulse energy, and sc aling to higher pulse energies will be straightforward. (C) 1999 Optical So ciety of America.