Irradiance map of an apertured Gaussian beam affected by coma

The Gaussian amplitude of a laser beam incident on an optical system affected by coma is expanded until the fourth order. This expansion is included in the Huygens–Fresnel integral calculation to obtain the amplitude and irradiance distribution on the focal plane of an optical system affected by coma. The analytical results obtained here are compared with a previous model of a comatic Gaussian beam. Appropriateness of the analytical model is also validated by the fitting with experimental data.