For the development of new kinds of refractive-index sensors for capillary electrophoresis, we investigated the scattering of an off-axis incident Gaussian beam by a homogeneous dielectric cylinder at normal incidence. The numerical calculations are based on the exact solution of the Helmholtz equation in circular cylindrical coordinates. Contrary to the procedures with geometrical and paraxial models, this procedure gives accurate results even when the beam dimensions are of the order of the wavelength of light and when the beam diameter is greater than the diameter of the dielectric cylinder. This rigorous electromagnetic treatment is verified by experimental measurements for cylinders with diameters from 5 to 100 μm.
© 1995 Optical Society of America
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