Shaper-assisted removal of the direction-of-time ambiguity in second-harmonic generation frequency-resolved optical gating

Abstract

We report on a practical method where a pulse shaper in combination with second-harmonic generation frequency-resolved optical gating (SHG-FROG) is used to fully characterize ultrashort laser pulses. The original pulse is modified by adding a small satellite, which allows us to determine the direction of time of the retrieved pulse. The setup extends the work of Zeek et al (2002 Appl. Phys. B 74 S265) to more arbitrary pulse structures. Moreover, it is demonstrated that the method is applicable also in high-power ultrashort laser systems, where the pulse former has to be placed before the chirped-pulse amplifier. We found that the amplitude of the satellite must be smaller than 20% of that of the original pulse to avoid nonlinear distortions.