We derive the analytical expression of the M2 factor of a Bessel–Gauss beam of any order and discuss its behavior for high and low values of the width of the Gaussian profile. The case of unapertured Bessel beams can be treated as a limiting case of our analysis.
© 1997 Optical Society of America
R. Borghi and M. Santarsiero, "M2 factor of Bessel Gauss beams," Opt. Lett. 22, 262-264 (1997)