We have developed a compact dispersion-free TG (transient-grating) FROG (frequency-resolved optical gating) by utilizing a mask that separates the input beam into three distinct beams focused into fused silica to create the FROG signal. Two of the beams are reflected off the same set of mirrors to ensure identical optical paths, eliminating the difficulty in establishing zero time delay between the beams. In addition, the use of only reflective optics avoids material dispersion in the FROG except for the mixing crystal. This TG FROG is capable of operating with an intensity of 1 × 1011 W/cm2 and has resolutions less than 0.5 and 1.3 fs for 25- and 10-fs input pulses, respectively.
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