Uses of Self-Focusing and Dispersion Effects in Time-Resolved Picosecond Spectroscopy

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Abstract
Experiments with single picosecond pulses have shown certain interesting effects in the transmission of pulses through various Kerr-active liquids, which prove useful in the study both of the laser pulses and of the liquid media. A technique is described for the accurate measurement of single-pulse intensities using three-photon fluorescence and the self-focusing effect. Using this technique it is possible to derive values of the effective Kerr constant for picosecond pulses. It is observed that the duration of the induced birefringence is not governed solely by the Debye reorientation time but also by other faster (·10−13-sec) mechanisms such as electron polarization or molecular ``rocking.'' The experimental results show that nitrobenzene and other molecules with relatively long Debye relaxation times have, under certain conditions, birefringence recovery times comparable to that of CS2. The experimental observations show that complete self-focusing is experienced by only a small portion of a laser pulse.

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