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.
Reference:
Litvin, I.A., Ngcobo, S., Naidoo, D., Ait-Ameur, K. and Forbes, A. 2014. Doughnut laser beam as an incoherent superposition of two petal beams. Optics Letters, 39, pp. 704-707
Litvin, I., Ngcobo, S., Naidoo, D., Ait-Ameur, K., & Forbes, A. (2014). Doughnut laser beam as an incoherent superposition of two petal beams. http://hdl.handle.net/10204/8915
Litvin, IA, Sandile Ngcobo, Darryl Naidoo, K Ait-Ameur, and A Forbes "Doughnut laser beam as an incoherent superposition of two petal beams." (2014) http://hdl.handle.net/10204/8915
Litvin I, Ngcobo S, Naidoo D, Ait-Ameur K, Forbes A. Doughnut laser beam as an incoherent superposition of two petal beams. 2014; http://hdl.handle.net/10204/8915.
Copyright: 2014 Optical Society of America. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item.For access to the full text item, please consult the publisher's website. The definitive version of the work is published in the Journal of Optics Letters, 39, pp. 704-707.
