Dielectric Metasurfaces for Complete Control of Phase and Polarization with Subwavelength Spatial Resolution and High Transmission (1411.1494v2)

Abstract: Metasurfaces are planar structures that locally modify the polarization, phase, and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurfaces have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here we show a metasurface platform based on high-contrast dielectric elliptical nano-posts which provides complete control of polarization and phase with sub-wavelength spatial resolution and experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase-plates, wave-plates, polarizers, beam-splitters, as well as polarization switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform.

• The paper introduces a novel dielectric metasurface that achieves complete control over phase and polarization using high-contrast elliptical nano-posts.
• The paper demonstrates transmission efficiencies ranging from 72% to 97% via a unitary and symmetric Jones matrix design.
• The paper enables independent wavefront shaping for orthogonal polarizations, reducing system complexity and offering compact optical solutions.

Overview of Dielectric Metasurfaces for Complete Control of Phase and Polarization

This paper introduces a novel metasurface platform that achieves comprehensive control over both the polarization and phase of transmitted light, maintaining high transmission efficiency even with subwavelength spatial resolution. Developed by researchers from the California Institute of Technology, this platform leverages high-contrast dielectric elliptical nano-posts to overcome limitations of previous metasurface designs, which either exhibited low transmission efficiency or restricted control over polarization and phase.

Dielectric Metasurfaces: Design and Capabilities

Metasurfaces are flat optical structures capable of manipulating light's phase, polarization, and amplitude. Unlike traditional optics, which rely on bulky elements, these metasurfaces offer a compact and customizable alternative by integrating into planar designs. The paper focuses on transmissive metasurfaces, where high transmission efficiencies are essential for practical applications.

This work employs a metasurface configuration of elliptical amorphous silicon posts. These posts exhibit birefringence, enabling varied phase shifts for different polarization components. The metasurface effectively samples the incident light wavefront and reshapes its phase and polarization. Using a unitary and symmetric Jones matrix at each metasurface pixel, the platform can handle any input light's polarization and phase distributions, achieving efficiencies from 72% to 97%.

Numerical Results and Observations

The research highlights several strong numerical results and experimental demonstrations:

1. Transmission Efficiency: The platform's average transmission efficiency exceeds 85%, with measured efficiencies ranging up to 97% while generating specific polarization and phase profiles.
2. Device Performance: The paper describes several fabricated devices, such as a polarization beam splitter focusing the $x$ and $y$ polarizations at distinct points, achieving efficiencies of 80% and 83%, respectively. Another device transforms incident Gaussian beams into Bessel-Gauss beams with high efficiency, showcasing the platform's versatility.
3. Independent Wavefront Control: It achieves distinct phase profiles for orthogonal polarization states, which traditionally require multiple optical components, reducing the system's complexity and size.

Practical and Theoretical Implications

The demonstrated metasurface platform has significant implications for optical systems design. The ability to exert complete control over light's polarization and phase makes it suitable for multiple optical applications, including beam steering, lenses, and holography, all in compact form factors. These devices are pertinent for fields demanding compact optics, such as wearable technology and integrated photonics systems.

Theoretically, the work on this metasurface reinforces the potential of dielectric materials in metasurface technology, challenging the dominance of plasmonic approaches that suffer from inherent efficiency constraints due to metal losses.

Future Developments

The platform paves the way toward further exploration of optical metasurface capabilities, notably in multi-functional and broadband optical components. Future research could enhance the operational bandwidth by exploring meta-atoms with nonlinear and active material properties. An exciting development trajectory involves metasurfaces on flexible substrates, potentially leading to conformal optics suitable for adaptive and dynamic optical applications.

In summary, this paper presents a significant advancement in metasurface technology, demonstrating their potential for efficient, versatile, and scalable optical manipulation, and setting a foundation for future innovations in integrated and flexible photonic systems.