On alternative methods for measuring the radius and propagation ratio of axially symmetric laser beams

Based on the developed efficient numerical methods for calculating the propagation of light beams, the alternative methods for measuring the beam radius and propagation ratio proposed in the international standard ISO 11146 are analysed. The specific calculations of the alternative beam propagation ratios M_i² performed for a number of test beams with a complicated spatial structure showed that the correlation coefficients c_i used in the international standard do not establish the universal one-to-one relation between the alternative propagation ratios M_i² and invariant propagation ratios M_σ² found by the method of moments.