Quantitative Nonlinear Optical Sum-Frequency Experiments using Incoherent Light

Abstract

Nonlinear optical sum‐frequency signals can be produced using pencils of incoherent light. The principal difficulty in making quantitative calculations of sum‐frequency power stems from the relatively low f‐number lens systems which must be used to focus light into the nonlinear crystal. For pencils of light with angular diameters between 0.05 and 0.5 rad, the most important factor which must be taken into account is the change in phase‐matching angle which occurs when the two interacting rays are not parallel. A graphical method which takes this factor into account is used to calculate the magnitude of nonlinear sum signal produced and its dependence upon crystal orientation. These calculations agree well with experimental measurements and show that the technique can be successfully applied to predict the results of a wide variety of sum‐frequency generation experiments utilizing incoherent light pencils.