An extension of the noncollinear second-harmonic generation technique for pulse autocorrelation measurements is described. A diffraction grating is used to produce a tailored, expanded beam, with a differential time delay along its expanded axis. When this beam is combined with an inverted replica of itself at the frequency-doubling crystal, the monitored spatial profile of the generated second-harmonic beam gives directly the duration of the incident laser pulse. A time resolution of better than 1 ps is obtained at 500 nm, and a total measurement range of∼80 ps. The optical system here described enables the extension of the measurement range in a simple manner.
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