PARTIAL-WAVE REPRESENTATIONS OF LASER-BEAMS FOR USE IN LIGHT-SCATTERING CALCULATIONS

In the framework of generalized Lorenz-Mie theory, laser beams are des cribed by sets of beam-shape coefficients. The modified localized appr oximation to evaluate these coefficients for a focused Gaussian beam i s presented. A new description of Gaussian beams, called standard beam s, is introduced. A comparison is made between the values of the beam- shape coefficients in the framework of the localized approximation and the beam-shape coefficients of standard beams. This comparison leads to new insights concerning the electromagnetic description of laser be ams. The relevance of our discussion is enhanced by a demonstration th at the localized approximation provides a very satisfactory descriptio n of top-hat beams as well.