Complete amplitude and phase control of light using broadband holographic metasurface (1706.09632v1)

Abstract: Reconstruction of light profiles with amplitude and phase information, called holography, is an attractive optical technique to display three-dimensional images. Due to essential requirements for an ideal hologram, subwavelength control of both amplitude and phase is crucial. Nevertheless, traditional holographic devices have suffered from their limited capabilities of incomplete modulation in both amplitude and phase of visible light. Here, we propose a novel metasurface that is capable of completely controlling both amplitude and phase profiles of visible light independently with subwavelength spatial resolution. The simultaneous, continuous, and broadband control of amplitude and phase is achieved by using X-shaped meta-atoms based on expanded concept of the Pancharatnam-Berry phase. The first experimental demonstrations of complete complex-amplitude holograms with subwavelength definition are achieved and show excellent performances with remarkable signal-to-noise ratio compared to traditional phase-only holograms. Extraordinary control capability with versatile advantages of our metasurface paves a way to an ideal holography, which is expected to be a significant advance in the field of optical holography and metasurfaces.

• The paper demonstrates a novel X-shaped metasurface that achieves independent modulation of light amplitude and phase.
• Experimental results reveal a 40% efficiency and a 211.3 signal-to-noise ratio, surpassing traditional phase-only techniques.
• Rigorous FEM simulations and analytical models confirm broadband operation across visible wavelengths, enabling high-resolution holographic imaging.

Complete Amplitude and Phase Control of Light Using Broadband Holographic Metasurface

The paper introduces a novel approach in the field of optical holography by demonstrating the potential of a holographic metasurface to attain full independent modulation of both the amplitude and phase of visible light with subwavelength spatial resolution. This capability addresses the limitations of conventional holographic devices, where modulation mechanisms inherently interfere, limiting precise control.

The authors propose the use of X-shaped meta-atoms, fabricated from poly-crystalline silicon, designed to expand upon the geometric or Pancharatnam-Berry phase. The primary contribution of the paper is the experimental realization of metasurfaces enabling complete complex-amplitude holograms with high definition and reduced noise, a significant enhancement over phase-only techniques.

The rigorous design of the structure, with each meta-atom constituted by two overlapping nanorods at different orientation angles, allows a full modulation range of amplitude and phase independently. These meta-atoms operate with a focus wavelength of 532 nm, showing efficiency standings at 40% for experimental and 49% for simulated outputs. The geometric phase properties also underlie the broadband capabilities of the metasurfaces, which remain consistent across varying wavelengths, confirmed by experimental demonstrations at 473 nm and 660 nm.

The paper presents robust evidence through rigorous theoretical analysis and numerical simulations using the finite element method (FEM). The FEM outcomes confirm the capacity of X-shaped structures to produce independent, high-efficiency modulation of amplitude and phase, adhering closely to theoretical predictions. Analytical models and experimental results align to showcase the metasurface's potential, suggesting an impressive signal-to-noise ratio of 211.3, an advancement beyond previous phase-only holographic methods.

Implications for this research are manifold. Practically, the metasurfaces designed demonstrate a pathway to high-resolution holographic imaging, potentially impacting fields such as 3D display technologies, optical data storage, and beyond. Theoretically, the development of such precise control of the electromagnetic wavefront paves the way for refinements in applications involving arbitrary beam shaping and optical computing.

Future developments may explore further material enhancements to optimize efficiency or expand the operational wavelength ranges to encompass applications within the infrared or terahertz spectrum. The scalability of the metasurface design also suggests potential applications in integrated optics, benefiting fields like nanophotonics and micro-optics.

This work delineates a significant advance in metasurface technology, harnessing the expanded geometric phase for novel applications while addressing classical hurdles in holographic imaging. As such, it opens new horizons for augmented control over light, extending the boundaries of existing optical devices and heralding a step towards impeccable control in holographic systems.