Photorefractive deflection technique using parallel and overlapping probe pump beams

Abstract

Most of the experimental work on photoacoustic (PA) and photothermal (PT) effects in gases, performed with the optical beam deflection technique, concerns either the propagation of a sound wave1 (thus probing the area far from the irradiated region), or the thermal properties of these gases2 (thus probing the boundary of the irradiated region with a probe beam crossing the pump beam). In this paper we report on an experimental study of a photorefractive deflection technique in which the probe beam used is principally inside the irradiated region. Our results are therefore a complement to the aforementioned works. To probe the interior of the irradiated region, no crossing of the probe and pump beams is allowed. Thus, in the present work, the two beams are parallel. This method can be used to align collinearly several cw laser beams to an error better than 3 µm.