Collinear type-II SHG-FROG pulse characterization in the sub-10-fs regime

Summary form only given. We demonstrate collinear type-II second harmonic based frequency resolved optical gating (SHG-FROG) in the sub-10-fs regime. Measurements on nJ pulses from an oscillator with a bandwidth corresponding to a transform limited pulse duration of 5.3 fs have been performed. Our apparatus is a modified version of a set-up used for the characterization of 20 fs pulses in the focus of a microscope objective. Our collinear type-II SHG-FROG offers the same advantages of this earlier demonstration whereas the modifications enable the measurement of even the broadest bandwidths currently available in the near infrared spectral region without the need for symmetrization of the FROG data or fringe removal by Fourier filtering. In our FROG set-up, we use a 10 /spl mu/m thick ADP crystal. This particular choice allows for a small residual group-velocity mismatch between the two fundamental pulses. Together with the usual bandwidth issues, this is the only limitation to the temporal resolution of the apparatus.