Techniques for the characterization of sub-10-fs optical pulses: a comparison

Several methods have been proposed for the phase and amplitude characteriza tion of sub-10-fs pulses with nJ energies. An overview of these techniques is presented, with a focus on the comparison of second-harmonic generation frequency-resolved optical gating (SHG-FROG) and spectral phase interferome try for direct electric-field reconstruction (SPIDER). We describe a collin ear FROG variant based on type-II phase-matching that completely avoids the geometrical blurring artifact and use both this and SPIDER for the charact erization of sub-10-fs Ti:sapphire laser pulses. The results of both method s are compared in an extensive statistical analysis. From this first direct experimental comparison of FROG and SPIDER, guidelines for accurate measur ements of sub-10-fs pulses are derived. We point out limitations of both me thods for pulses in this ultrashort pulse regime.