The far-field of the linearly polarized Gaussian beams diffracted at a circular aperture can be expressed as a sum of two orthogonal transversal electric (TE) and transversal magnetic (TM) terms. According to the far-field energy flux distributions of the TE and TM terms, the analytical expressions of the power of the TE and TM terms for the Gaussian diffracted beam are derived, which allow one to examine the ratios of the power of the TE and TM terms to the whole beam power. Based on the definition of the second-order moment of the far-field energy flux distributions, the analytical formulae of the far-field divergence angles of the Gaussian diffracted beam and its TE and TM terms are obtained, as well as the relationship among those far-field divergence angles. The influences of the f-parameter and the truncation parameter on the far-field divergence angles are analyzed. With the increase of the f-parameter, the far-field divergence angles first increase and finally tend to their respective saturated values. The influence of the truncation parameter on the far-field divergence angles is related to the f-parameter. When the f-parameter is relatively large, the effect of the truncation parameter on the far-field divergence angles is not distinct. When the f-parameter is moderate, the far-field divergence angles first decrease and finally tend to their respective minimum values with increasing the truncation parameter. When the f-parameter is relatively small, the far-field divergence angles of the Gaussian diffracted beam and its TM term fluctuate in a certain degree with varying the truncation parameter.
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