Laboratory determination of beam-shape coefficients for use in generalized Lorenz-Mie theory

The use of the generalized Lorenz-Mie theory (GLMT) requires knowledge of beam-shape coefficients (BSC's) that describe the beam illuminating a spherical scatterer. We theoretically demonstrated that these BSC's can be determined from an actual beam in the laboratory. We demonstrate the effectiveness of our theoretical proposal by determining BSC's for a He-Ne laser beam focused to a diameter of a few micrometers. Once these BSC's are determined, the electromagnetic fields of the illuminating beam may be evaluated. By relying on the GLMT, we can also determine all properties of the interaction between beam and scatterer, including mechanical effects (radiation pressures and torques). (C) 2001 Optical Society of America.