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 nonlinear media. Negative nonlinear phase shifts are generated by phase-mismatched second-harmonic generation, and the phase-modulated pulses are then compressed by propagation through materials with normal dispersion. Millijoule-energy pulses from a Ti:sapphire amplifier are compressed from 120 to 30 fs, and calculations indicate that compression ratios of >10 are realistically achievable by use of this approach with optimal materials. The insertion loss of the compressor can be less than 10% of the pulse energy, and scaling to higher pulse energies will be straightforward.