  Using an analytical expression for an integral involving Bessel and Legendre
functions we succeeded to obtain the partial wave decomposition of a general
optical beam at an arbitrary location from the origin. We also showed that the
solid angle integration will eliminate the radial dependence of the expansion
coefficients. The beam shape coefficients obtained are given by an exact
expression in terms of single or double integrals. These integrals can be
evaluated numerically in a short time scale. We presented the results for the
case of linear polarized Gaussian beam.
