Temporal characterization of ultrashort pulses at the focus of a high numerical aperture objective

Summary form only given. Precise characterization of focused pulses is required to produce optimal images with multiphoton microscopes. We used collinear type II second-harmonic generation frequency-resolved optical gating (SHG FROG) to measure the pulse intensity and phase at the focus of a Zeiss CP-Achromat 100/spl times/, 1.25 NA, infinity-corrected oil objective, and accurately retrieved 20 fs pulses.