Frequency-resolved optical grating using surface third-harmonic generation

Summary form only given. Frequency-resolved optical grating (FROG) based on polarization-gate (PG FROG) and second-harmonic generation (SHG FROG) have been used successfully to characterize ultrashort optical pulses from the infrared to the ultraviolet. We extend this FROG technique with the use of third-harmonic generation (THG FROG) on the surface of virtually any substrate that transmits the fundamental wavelength. Unlike SHG FROG where the presence of the time-reversal ambiguity resulted in traces that are somewhat unintuitive, the third-order process of THG is unambiguous therefore the resulting THG FROG trace is as appealing as the popular PC FROG. We used a femtosecond Ti:sapphire laser oscillator.