Doughnut laser beam as an incoherent superposition of two petal beams

Abstract

Laguerre–Gaussian beams with a nonzero azimuthal index are known to carry orbital angular momentum (OAM), and are routinely created external to laser cavities. The few reports of obtaining such beams from laser cavities suffer from inconclusive evidence of the real electromagnetic field. In this Letter we revisit this question and show that an observed doughnut beam from a laser cavity may not be a pure Laguerre–Gaussian azimuthal mode but can be an incoherent sum of petal modes, which do not carry OAM. We point out the requirements for future analysis of such fields from laser resonators.

© 2014 Optical Society of America

Generation of a vector doughnut beam from an internal mirror He–Ne laser

Sunil Vyas, Yuichi Kozawa, and Shunichi Sato
Opt. Lett. 39(7) 2080-2082 (2014)

Angular self-reconstruction of petal-like beams

Igor A. Litvin, Liesl Burger, and Andrew Forbes
Opt. Lett. 38(17) 3363-3365 (2013)

Controlling the handedness of directly excited Laguerre–Gaussian modes in a solid-state laser

Di Lin, J. M. O. Daniel, and W. A. Clarkson
Opt. Lett. 39(13) 3903-3906 (2014)

Measurement of the orbital angular momentum density of Bessel beams by projection into a Laguerre–Gaussian basis

Christian Schulze, Angela Dudley, Robert Brüning, Michael Duparré, and Andrew Forbes
Appl. Opt. 53(26) 5924-5933 (2014)

Revisiting the which-way experiment with twisted light beams

Lixiang Chen, Wuhong Zhang, Kai Cai, Yuanying Zhang, and Qianqian Qi
Opt. Lett. 39(20) 5897-5900 (2014)