Determination of the topological charge of a twisted beam with a Fresnel bi-prism

Olivier Emile (1) , Janine Emile (2) , Christian Brousseau (3)

1 URU 435 LPL - URU 435 Laboratoire de physique des lasers
2 IPR - Institut de Physique de Rennes
3 IETR - Institut d'Électronique et des Technologies du numéRique

The self-interference pattern of a Laguerre Gaussian beam using a Fresnel bi-prism is shown to be very different from what could be expected from a usual laser beam. Actually it resembles the interference pattern that could be obtained using a double slit experiment. The interferences are shifted and the topological charge and its sign can be readily determined considering the shift order of the pattern only. However, since there is no diffraction nor absorption loses unlike in a double slit interference, such a set up could be used even for low power twisted beams or beams with high topological charge. Even fractional topological charges could be determined with an absolute precision of 0.05.

Mots clés: topological charge determination; twisted beams; Fresnel bi-prism; interference

Domaines: Optique [physics.optics]

Olivier Emile, Janine Emile, Christian Brousseau. Determination of the topological charge of a twisted beam with a Fresnel bi-prism. Journal of Optics, 2014, Journal of Optics, 16 (12), pp.125703. ⟨10.1088/2040-8978/16/12/125703⟩. ⟨hal-01076845⟩