Dynamic multilevel spiral phase plate generator

M Caño-García,M A Geday,J M Otón,X Quintana

doi:10.1038/s41598-018-34041-2

M Caño-García, M A Geday + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-34041-2

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Journal: Scientific Reports	Publication Date: Oct 25, 2018
Citations: 35	License type: open-access

Affiliation: Universidad Politécnica de Madrid

Abstract

The design and characterisation of a reconfigurable multi-level spiral phase plate is shown. The device is based on a pie-shape liquid-crystal structure with 24 slices driven by custom electronics that allow independent excitation control of each electrode. The electrooptical cell was manufactured using maskless laser ablation lithography and has shown an unprecedented high fill factor. The topological charge can be dynamically changed between 1, 2, 3, 4, 6, 8 and 12. The device has been calibrated and characterised at 632.8 nm but can be employed at any wavelength in the visible and near infrared spectrum, just modifying the driving parameters of the electrodes. The experimental results have been compared to predictions derived from simulations. An excellent correspondence between theoretical and experimental result has been found in all cases.

Highlights

Optical vortices were first mentioned in the pioneering work of Nye and Berry[1] in the 70’s and the first reports on generation of optical vortices were published two decades later[2,3]
An optical vortex is characterised by its orbital angular momentum or topological helical charge, l, which may take any integer non-zero number, and is equivalent to the number of entwined helices describing the wavefront
An liquid crystal (LC) cell consists of two opposing transparent ITO electrodes treated with an alignment agent, separated by spacers

Summary

Introduction

Optical vortices were first mentioned in the pioneering work of Nye and Berry[1] in the 70’s and the first reports on generation of optical vortices were published two decades later[2,3]. Each of these phase plates convert a planar wavefront into an integer number of entwined helices, an optical vortex (Fig. 2). An optical vortex is characterised by its orbital angular momentum or topological helical charge, l, which may take any integer non-zero number, and is equivalent to the number of entwined helices describing the wavefront. Positive and negative values of l describe the handedness of the helices: righthanded vortices are conventionally assigned to positive helical charge

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