Photorefractive deflection technique using parallel and overlaping probe and pump beams

The present work provides an experimental study of a pulsed photorefractive technique to diagnose the interior of an irradiated region. Results obtained in a mixture of SF6 and Ar are presented to illustrate the experimental technique. Three distinct areas have been studied, (i) The two beams are parallel and their optical axes are coincident (collinear). At this particular position, the probe beam suffers a defocusing effect that is used to align collinearly two laser beams with a precision of ±3 μm. (ii) The two beams are parallel but slightly off axis. In this case, the probe beam suffers a deviation that is the sole result of a rarefaction in the irradiated region followed by the normal thermal equilibration. (iii) The two beams are parallel and slightly overlapping. The probe beam suffers a deviation similar to the preceding one. Moreover, it sees an initial outward-propagating acoustic (density) wave. It is in this particular region that the acoustic perturbation appears. Finaly, the gas mixture use...