Abstract

We examine beam pointing fluctuations that arise when the Stokes field is initiated from vacuum fluctuations. Using a model that includes diffraction and pump depletion, we use stochastic boundary conditions to solve for the fields. We present results with one and two transverse coordinates and compare them with experimental observations. Using a Gaussian input pump beam, we find that δK, a measure of the transverse fluctuations, is essentially a linear function of Fresnel number, in both the linear and nonlinear regimes, with larger values in the latter case. For low Fresnel numbers, we find that our theory is in excellent agreement with experiment when one or two transverse coordinates are used. For larger Fresnel numbers, quantitative agreement with experiment is obtained only if both transverse coordinates are employed in the calculation.

© 1992 Optical Society of America