A detailed study of the effect of laser coherence on thermal grating by a novel polarization arrangement of the incident laser beams

Abstract

We have studied the effect of laser coherence on thermal grating by measuring the dependence of the thermal grating on the relative time delay between pump beams. We employed a novel polarization arrangement of the incident laser beams, so that any change of the beam quality and the beam direction during the variation of the relative time delay could not affect the experimental accuracy. Our results agree quite well with the prediction based on a sixth-order coherence function theory. Since our method resembles the polarization rotation method suggested by Hamilton et al. [Optics Lett. 4 (1979) 124], this experiment provides a good example of the feasibility of this novel technique. This new method can also be used to obtain information on both pulse coherence and pulse duration of an ultrashort laser pulse.