Full-color complex-amplitude vectorial holograms based on multi-freedom metasurfaces (1912.11184v1)

Abstract: Phase, polarization, amplitude and frequency represent the basic dimensions of light, playing crucial roles for both fundamental light-mater interactions and all major optical applications. Metasurface emerges as a compact platform to manipulate these knobs, but previous metasurfaces have limited flexibility to simultaneous control them. Here, we introduce a multi-freedom metasurface that can simultaneously and independently modulate phase, polarization and amplitude in an analytical form, and further realize frequency multiplexing by a k-space engineering technique. The multi-freedom metasurface seamlessly combine geometric Pancharatnam-Berry phase and detour phase, both of which are frequency-independent. As a result, it allows complex-amplitude vectorial hologram at various frequencies based on the same design strategy, without sophisticated nanostructure searching of massive size parameters. Based on this principle, we experimentally demonstrate full-color complex-amplitude vectorial meta-holograms in the visible with a metal-insulator metal architecture, unlocking the long-sought full potential of advanced light field manipulation through ultrathin metasurfaces.

• The paper introduces a multi-freedom metasurface that combines geometric Pancharatnam-Berry and detour phases for independent modulation of phase, amplitude, and polarization.
• The research employs a diatomic MIM architecture to decouple spectral responses, yielding high diffraction efficiency and robust frequency multiplexing in experimental setups.
• Reconstructed holographic images exhibit enhanced clarity and minimal crosstalk, indicating promising applications in high-fidelity displays and quantum communication.

Full-Color Complex-Amplitude Vectorial Holograms Based on Multi-Freedom Metasurfaces

The development of metasurfaces has provided remarkable opportunities for manipulating light in multiple dimensions, including phase, amplitude, polarization, and frequency. Such manipulation can lead to new mechanisms of light-matter interaction and open avenues for advanced optical applications. The discussed research introduces a multi-freedom metasurface capable of simultaneously and independently modulating phase, polarization, and amplitude and achieving frequency multiplexing through a k-space engineering approach. This metasurface integrates geometric Pancharatnam-Berry (P-B) phase and detour phase, both independent of frequency, enabling complex-amplitude vectorial holograms viewable across various frequencies without necessitating complex nanostructure searches.

Technical Approach and Experimental Implementation

The proposed multi-freedom metasurface is designed with a diatomic structure that synthesizes P-B and detour phases, offering a collaborative control over vast degrees of freedom. This design facilitates broad and independent manipulation of multiple optical dimensions within a single metasurface. Operational within the visible light spectrum, the metasurface employs a metal-insulator-metal (MIM) architecture comprising aluminum nanorods atop a silicon dioxide spacer, configured to enhance diffraction efficiencies significantly.

A central feature of the metasurface is its employment of uniformly-sized meta-elements that decouple P-B and detour phase controls from spectral responses, thus supporting versatile and robust broadband applications. The metasurface not only manages phase, amplitude, and polarization but also conducts frequency multiplexing, allowing distinct holographic information to be encoded and spatially reconstructed at different wavelengths.

The experimental results substantiate this multi-freedom metasurface's potential by demonstrating full-color complex-amplitude vectorial meta-holograms in visible light. Diffraction efficiencies were optimized, achieving a significant degree of control as the metasurface operates predominantly in the -1 diffraction order, further enabling advanced frequency multiplexing through grating dispersion.

Results and Implications

Experimentation showcased that illuminating the metasurface with RGB beams produced distinct holographic images with minimal crosstalk, demonstrating the metasurface's precedence in versatility and efficiency over prior designs in both theoretical and practical terms. The reconstructed images from complex-amplitude holograms displayed superior clarity and smoothness compared to traditional phase-only holograms, corroborating the enhanced fidelity achievable through simultaneous phase and amplitude modulation. Additionally, the capacity to encode dual full-color images oriented orthogonally in polarization exemplifies profound implications in optical multiplexing and information security.

The versatility of integration with different material configurations, like high-efficiency all-dielectric transmission metasurfaces, underscores the adaptability of the multi-freedom design. Its identified applications in high-fidelity displays, quantum technologies, and vectorial field reconstitution render it an essential advancement within the optical engineering domain.

Future Prospects

The demonstrated multi-freedom metasurface suggests substantial advancements in light manipulation technologies. Potential developments might see incorporation into quantum communication protocols, optimized polarization control devices, and novel encryption systems based on complex light fields. Future work may also expand this framework to metasurfaces crafted from novel materials, enhancing efficiency and broadening the operational spectral ranges. The foundational principles elucidated in this research could substantively influence subsequent metasurface applications across diverse scientific and technological fields.