Non-linear optical effects in liquids

Abstract

Recent advances in the field of non-linear optical phenomena are reviewed in which particular reference is made to those effects induced within liquid media.Several aspects of this field of study were experimentally investigated. In particular, direct quantitative examinations were made of the intensity dependent refractive index modulations (associated with the phenomena of stimulated light scattering) induced in both absorbing and non-absorbing liquids by the intense light fields from a pulsed ruby laser. A probe technique, which facilitated both spatial and temporal analyses of this induced non-linearity, was developed, in which the output from a continuous argon ion laser was Bragg reflected off the induced structure within the liquid. The experimental and theoretical results are shown to be consistent and values for the thermal relaxation time of liquids are determined.Qualitative aspects of the non-linear phenomena of self trapping and de-focusing of laser light are considered with particular emphasis placed on the effects of self-bending and the interaction of self-trapped light beams.Studies were conducted into the effect of intense laser light on saturable absorbers. The intensity dependent blue fluorescence observed from these absorbers when excited by ruby laser light resulted from excited state absorption to the second singlet state. The intensity dependence also indicated the power density required to saturate the first excited singlet state for each dye. A similar fluorescence due to two photon absorption was observed in certain solvents.The residual population inversion characteristics of ruby were examined using a stimulated light scattering feedback technique. The results of these investigations are shown to be in qualitative agreement with current theories.