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Vortex beams with tunable "all-with-visible-light" dye-doped liquid crystal q-plates for broadband application

Adrián Moya, Adriana R. Sánchez-Montes, Sergi Gallego, Eva M. Calzado, Andrés Márquez, Inmaculada Pascual, Augusto Beléndez

Abstract

The photoalignment technique for liquid crystal (LC) device fabrication, despite being a well-established method, remains of significant relevance because of its broad applicability. Among its applications, one of particular interest is the generation of structured light, specifically the manufacturing of Pancharatman-Berry (PB) devices, capable of generating optical vortices with angular momentum. In this work, we propose a thorough theoretical and experimental analysis of the optical response of dye-doped liquid crystal (DDLC) devices by examining their performance in terms of tunability and achromaticity across the whole visible spectrum, considering diattenuation effects and how they affect the efficiency of the devices. We experimentally demonstrate the fabrication of photoaligned devices in the visible range with 532 nm laser light and the robust generation of high-quality optical vortices, achieved by a straightforward and accessible technique using a commercial Variable Spiral Plate (VSP), avoiding the need for complex rotational systems or programmable spatial light modulators. Our results demonstrate that diattenuation effects do not prevent the functionality of the devices across the whole visible spectrum and with extended ranges of achromaticity.

Vortex beams with tunable "all-with-visible-light" dye-doped liquid crystal q-plates for broadband application

Abstract

The photoalignment technique for liquid crystal (LC) device fabrication, despite being a well-established method, remains of significant relevance because of its broad applicability. Among its applications, one of particular interest is the generation of structured light, specifically the manufacturing of Pancharatman-Berry (PB) devices, capable of generating optical vortices with angular momentum. In this work, we propose a thorough theoretical and experimental analysis of the optical response of dye-doped liquid crystal (DDLC) devices by examining their performance in terms of tunability and achromaticity across the whole visible spectrum, considering diattenuation effects and how they affect the efficiency of the devices. We experimentally demonstrate the fabrication of photoaligned devices in the visible range with 532 nm laser light and the robust generation of high-quality optical vortices, achieved by a straightforward and accessible technique using a commercial Variable Spiral Plate (VSP), avoiding the need for complex rotational systems or programmable spatial light modulators. Our results demonstrate that diattenuation effects do not prevent the functionality of the devices across the whole visible spectrum and with extended ranges of achromaticity.
Paper Structure (17 sections, 19 equations, 10 figures, 3 tables)

This paper contains 17 sections, 19 equations, 10 figures, 3 tables.

Table of Contents

  1. INTRODUCTION
  2. THEORY
  3. Geometric phase and diattenuation
  4. Spatially variant neutral lines devices
  5. $\theta(r,\varphi)=\varphi$.
  6. $\theta(r, \varphi)=\varphi+\frac{\pi}{2}$.
  7. SAMPLE PREPARATION AND EXPERIMENTAL SETUP
  8. RESULTS
  9. Tunability
  10. Achromaticity
  11. CONCLUSIONS
  12. ACKNOWLEDGEMENTS
  13. AUTHOR DECLARATIONS
  14. Conflict of Interest
  15. Author Contributions
  16. ...and 2 more sections

Figures (10)

  • Figure 1: Output beam from the photoaligned device, where two different wavefronts overlap each other: a planar wavefront and a helical wavefront, each of them associated to the two orthogonal circularly polarized states. If the input beam has RHC polarization, then the optical vortex will have LHC polarization, and the planar wavefront RHC polarization.
  • Figure 2: Photoalignment setup.
  • Figure 3: Characterization setup.
  • Figure 4: Laboratory scaled simulation of the optical vortices generated by our photoaligned q-plate, where (a) shows the phase profile generated by a q-plate with topological charge 2 and (b-d) are the optical vortices obtained when the incident wavelegnth is 473 nm, 532 nm and 633 nm, respectively, at the focal plane of lens L2.
  • Figure 5: q-plate of 7.4 µ m thickness between crossed polarizers.
  • ...and 5 more figures