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arXiv · 1407.0065

Achromatic orbital angular momentum generator

Frédéric Bouchard·Harjaspreet Mand·Mohammad Mirhosseini·Ebrahim Karimi·Robert W. Boyd
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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.

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Frédéric Bouchard, Harjaspreet Mand, Mohammad Mirhosseini, Ebrahim Karimi, Robert W. Boyd. 2014-11-06. Achromatic orbital angular momentum generator. https://doi.org/10.1088/1367-2630%2F16%2F12%2F123006

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