Parametric Study of Apertured Focused Gaussian Beams

Using Fresnel diffraction integrals, calculations have been made of the irradiance and power distributions in the near field and in the vicinity of the focus for Gaussian beams focused through annular apertures. Universal curves have been plotted which display the calculations in terms of dimensionless parameters. For very large focal length infrared systems it has been found that the irradiance distribution is not symmetrical about the geometrical focal plane as is commonly assumed. Gaussian and sinusoidal phase aberrations in the aperture field have been included.