autocorrelateur photoacoustic

Autocorrélateur à absorption 2 photons acousto-optic.
A single-shot autocorrelation of an ultrashort UV pulse is measured by detecting a two-photon-induced photoacoustic signal in water. A supersonic wave representing the autocorrelation function is detected by a polyvinylidene fluoride piezoelectric film with a spatial resolution of less than 60 microm. The detection sensitivity is higher than that of a multiphoton-induced fluorescence method by approximately 2 orders of magnitude.

By excitation of cadmium vapor with a high-peak-power KrF excimer laser pulse, fluorescence of an atomic transition at lambda = 508 nm is induced by a two-photon ionization process followed by fast recombination. The nonlinear response of the medium is used to develop a simple single-shot autocorrelator for subpicosecond KrF excimer laser pulses operating down to intensities of less than 10(9)W/cm.(2) We have measured 360-fs (FWHM) pulses at lambda = 248 nm with a time resolution of 15 fs.

A single-shot autocorrelator based on the two-photon excited fluorescence of BaF(2) in the visible region at 400 nm has been developed for ultrashort KrF laser pulses at 248 nm. Operation in the visible region offers simplification in the required optical components as compared with previously reported systems, which used ultraviolet fluorescence emission. The fluorescence intensity is also used to measure the two-photon absorption coefficient of BaF(2), yielding a value of ? = 1.3 ± 0.4 × 10(-10) cm/W.

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