Dielectric Metasurfaces for Complete and Independent Control of Optical Amplitude and Phase (1903.00578v2)

Abstract: Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light. Here, we present an approach, simple in concept and in practice, that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies. This opens up applications in computer-generated holography, allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography. We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two- and three-dimensional holographic objects. We show that phase-amplitude metasurfaces enable a few features not attainable in phase-only holography; these include creating artifact-free two-dimensional holographic images, encoding phase and amplitude profiles separately at the object plane, encoding intensity profiles at the metasurface and object planes separately, and controlling the surface textures of three-dimensional holographic objects.

• The paper demonstrates a novel dielectric metasurface platform that enables arbitrary, dual-frequency amplitude and phase control via engineered birefringent meta-atoms.
• The paper achieves high holographic fidelity by eliminating artifacts through combined amplitude-phase modulation, outperforming traditional phase-only approaches.
• The proposed design is extendable to visible frequencies and is compatible with CMOS processes, highlighting its potential for diverse optical applications.

Comprehensive Analysis of Dielectric Metasurfaces for Optical Amplitude and Phase Control

This paper presents a significant advancement in the field of optical metasurfaces, specifically targeting the independent control of optical amplitude and phase using dielectric metasurfaces. The approach is rooted in engineering meta-atoms with varying form birefringence and rotation angles to achieve high-efficiency dielectric metasurfaces that simultaneously influence both amplitude and phase at one or two optical frequencies. This development opens pathways for enhanced capabilities in computer-generated holography, eliminating the need for complex iterative algorithms typically required for phase-only holography.

Key Contributions and Results

The paper delineates several core contributions:

1. Dual-Frequency Amplitude and Phase Control: The authors introduce a metasurface platform enabling arbitrary and simultaneous control of both amplitude and phase at telecommunication frequencies. This is achieved through birefringent meta-atoms that convert LCP to RCP light, whereby amplitude is governed by birefringence degree and phase by in-plane meta-atom orientation.
2. Efficiency of Dielectric Metasurfaces: The dielectric metasurfaces are demonstrated to yield high efficiency in controlling wavefronts without the inherent losses associated with metallic metasurfaces.
3. Holographic Performance: Comparing phase-amplitude (PA) metasurfaces to phase-only (PO) ones, the paper reports that PA metasurfaces produce artifact-free holographic images, with notable success in rendering complex 3D holographic objects with distinct textures.
4. Extension to Visible Frequencies and CMOS Compatibility: The methodology is shown to be easily extendable to the visible spectrum and compatible with CMOS fabrication processes.

Significant numerical results include achieving amplitude conversion between 0 and 1 through precise control of birefringence, and achieving high fidelity in holographic reconstructions both through simulations and physical experiments. Notably, the approach enables the encoding of both amplitude and phase independently, providing a higher degree of control over the holographic images produced.

Implications and Future Directions

The implications of this research are multifaceted, impacting theoretical understanding and practical applications:

• Theoretical Implications: This work provides a refined lens through which to consider the control of optical properties independently, potentially influencing the development of new metasurface design frameworks.
• Practical Applications: Immediate applications are seen in areas demanding precise optical manipulation, including holography and imaging systems, optics for augmented reality devices, and enhancement of optical communication systems.

Looking forward, this research invites further exploration into multi-frequency control and the potential for applications beyond the telecom band, moving towards accommodating broader optical spectra, including ultraviolet and infrared.

Additionally, future research could delve into optimizing fabrication techniques further to improve the structural integrity and functional efficiency of metasurfaces across larger areas and more complex environments.

In conclusion, this paper represents a substantial methodological contribution to the field of metasurfaces, with potential for vast applications and further theoretical exploration in optics and beyond.