Propagation of a Cavity-Dumped CO2Laser Pulse through SF6

Abstract

Coherent interactions between short C${\mathrm{O}}_2$ laser pulses and a resonant absorbing S${\mathrm{F}}_6$ gas medium have been examined carefully, using a laser cavity-dumped rectangular pulse with a width of 20 nsec and input intensities from 10 to ${10}^4$ W/${\mathrm{cm}}^2$. Parameters studied included the width, shape, and delay time of the transmitted pulse after propagation through several absorption lengths of S${\mathrm{F}}_6$ cell. In addition to these measurements, we have observed two new phenomena, namely, optical free induction decay and edge echo, which are induced by this short rectangular C${\mathrm{O}}_2$ laser input pulse. Results indicate that although level degeneracy in S${\mathrm{F}}_6$ may be involved, the simple two-level model can account qualitatively for most observed phenomena, with the exception that the observed shape of a $2\pi$ pulse deviates significantly from the symmetric hyperbolic-secant function predicted by the simple two-level theory. In the $\pi$ pulse region, we have demonstrated that the free-induction-decay tail can be valuable for studies of atomic and molecular collision processes.