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Generation of Perfectly Achromatic Optical Vortices Using a Compensated Tandem Twisted Nematic Cell

Dmytro O. Plutenko, Mikhail V. Vasnetsov

TL;DR

This work addresses the challenge of generating perfectly achromatic optical vortices under white-light illumination. It introduces a compensated tandem twisted nematic (TN) liquid-crystal device and a rigorous Jones-matrix model to analyze chromatic fidelity, explicitly accounting for non-adiabatic Mauguin deviations and manufacturing tolerances. Three compensation strategies are proposed, including an active tunable-retarder scheme that can suppress parasitic amplitude modulation, enabling broadband, high-phase-purity vortex generation; passive and narrow-band strategies offer practical alternatives. The results establish the compensated tandem TN cell as a powerful platform for high-fidelity white-light singular optics with potential applications in static vortex generation and full complex-amplitude spatial light modulation.

Abstract

The generation of white optical vortices is currently constrained by intrinsic trade-offs between spectral bandwidth, conversion efficiency, and temporal pulse integrity in conventional diffractive and geometric-phase approaches. In this work, we theoretically investigate a compensated tandem crossed twisted nematic (TN) liquid crystal architecture that overcomes these fundamental limitations. By developing a rigorous Jones matrix model and defining specific figures of merit for chromatic fidelity, we analyze the impact of manufacturing imperfections and non-adiabatic waveguiding (deviations from the Mauguin regime) on the device performance. We propose and evaluate three distinct compensation strategies, ranging from optimized passive designs for specific manufacturing tolerances to a robust active compensation scheme utilizing a tunable retarder. Our analysis demonstrates that the active approach effectively nullifies parasitic amplitude modulation, enabling the generation of perfectly achromatic vortices with high phase purity across an arbitrary bandwidth. This establishes the compensated tandem TN cell as a superior and versatile platform for high-fidelity white-light singular optics.

Generation of Perfectly Achromatic Optical Vortices Using a Compensated Tandem Twisted Nematic Cell

TL;DR

This work addresses the challenge of generating perfectly achromatic optical vortices under white-light illumination. It introduces a compensated tandem twisted nematic (TN) liquid-crystal device and a rigorous Jones-matrix model to analyze chromatic fidelity, explicitly accounting for non-adiabatic Mauguin deviations and manufacturing tolerances. Three compensation strategies are proposed, including an active tunable-retarder scheme that can suppress parasitic amplitude modulation, enabling broadband, high-phase-purity vortex generation; passive and narrow-band strategies offer practical alternatives. The results establish the compensated tandem TN cell as a powerful platform for high-fidelity white-light singular optics with potential applications in static vortex generation and full complex-amplitude spatial light modulation.

Abstract

The generation of white optical vortices is currently constrained by intrinsic trade-offs between spectral bandwidth, conversion efficiency, and temporal pulse integrity in conventional diffractive and geometric-phase approaches. In this work, we theoretically investigate a compensated tandem crossed twisted nematic (TN) liquid crystal architecture that overcomes these fundamental limitations. By developing a rigorous Jones matrix model and defining specific figures of merit for chromatic fidelity, we analyze the impact of manufacturing imperfections and non-adiabatic waveguiding (deviations from the Mauguin regime) on the device performance. We propose and evaluate three distinct compensation strategies, ranging from optimized passive designs for specific manufacturing tolerances to a robust active compensation scheme utilizing a tunable retarder. Our analysis demonstrates that the active approach effectively nullifies parasitic amplitude modulation, enabling the generation of perfectly achromatic vortices with high phase purity across an arbitrary bandwidth. This establishes the compensated tandem TN cell as a superior and versatile platform for high-fidelity white-light singular optics.

Paper Structure

This paper contains 31 sections, 108 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Theoretical Model
  3. Light Propagation in a Single Twisted Nematic Cell
  4. The Ideal Tandem Cell as an Achromatic Rotator
  5. Analysis of a Non-Ideal Tandem Cell
  6. Perturbation Model and Small Parameters
  7. Transmission Analysis and Filtering of Parasitic Components
  8. Figures of Merit for Non-Achromaticity
  9. Amplitude Non-Achromaticity ($\mathcal{A}$)
  10. Phase Non-Achromaticity
  11. Non-Achromaticity of the Non-Ideal Tandem Cell
  12. Compensation Strategies and Discussion
  13. Mitigation of Non-Idealities: The Compensated System Model
  14. Strategy A: Active Compensation for Full Achromaticity
  15. Strategy B: Passive Compensation with a Quarter-Wave Plate
  16. ...and 16 more sections

Figures (5)

  • Figure 1: Configuration of the tandem TN cell system.
  • Figure 2: Numerical validation of the theoretical model for a non-ideal tandem cell
  • Figure 3: Schematic of the proposed optical setup for the generation and filtering of optical vortices.
  • Figure 4: Numerical verification of the active compensation strategy (Strategy A).
  • Figure 5: Comparative analysis of the figures of merit for the proposed compensation strategies.