Achromatic orbital angular momentum generator

Abstract

We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarisation, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of $95\%$ for these three different wavelengths is observed. %, which confirms its wavelength independence. This device may be used to generate a white vector vortex beam, as we show, and may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed.

15 pages, 6 figures and 1 table

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Cited by in corpus (11)

• Geometric phase from Aharonov-Bohm to Pancharatnam-Berry and beyond
• Spin-to-orbital angular momentum conversion in dielectric metasurfaces
• Arbitrary optical wavefront shaping via spin-to-orbit coupling
• Bragg-Berry mirrors: reflective broadband q-plates
• Topological features of vector vortex beams perturbed with uniformly polarized light
• Vectorial vortex generation and phase singularities upon Brewster reflection
• Scalar vortex coronagraph mask design and predicted performance
• OAM beams from incomplete computer generated holograms
• Electrons in intense laser fields with local phase, polarization, and skyrmionic textures
• Multi-wavelength Q-plate Arithmetic in an All-Liquid-Crystal Modular Setup
• Squeezing of X waves with orbital angular momentum