Phase Manipulation of Electromagnetic Waves with Metasurfaces and Its Applications in Nanophotonics

Abstract

elements. Thus, realizing phase manipulation of EM waves at the nanoscale has become a key pursuit for the development of modern optics and nanophotonics.Metamaterials are 3D artificial nanostructures composed of periodic subwavelength unit cells that resonantly couple to the incident EM waves, exhibiting effective electric and magnetic responses not found in nature. [1][2][3] However, these promising potential applications are hindered in their applications due to the challenges of fabricating the required complex 3D nanostructures and the inherent metallic losses and strong dispersion of plasmonic elements at optical frequencies. Planar metamaterials, or so-called metasurfaces, can be fabricated using existing technologies, such as the lithography method and have attracted increasing attention due to their feasibility, low loss, and ease of fabrication. [4,5] The most prominent advantage of metasurfaces is that they can generate spatial phase discontinuities over the full 2π range with an optically thin interface; moreover, the resolution is less than one wavelength. Thus, wavefronts can be shaped with a distance of much less than the wavelength. With the increasing development of metasurfaces, the aforementioned limitations can be solved using various ultrathin optical devices, which have properties superior to their conventional counterparts. [6][7][8][9][10][11][12] Here, we concentrate on the new capabilities of metasurfaces in recent years in manipulating the phase and propagation behaviors of EM waves. In Section 2, we briefly introduce the underlying mechanisms of three types of phase discontinuities. In Section 3, we review the basic applications of phase modulation using metasurfaces. In Section 4, we review more complex and advanced information photonics that have emerged from metasurfaces. In the last section, we provide concluding remarks and an outlook on future development directions. Three Basic Types of Phase Discontinuities Generated by Metasurfaces Resonance PhaseThe pioneering approach to achieve phase discontinuities was to use the dispersion of various metallic nanoantennas, as shown in the left panel of Figure 1a. The optical energy is coupled to surface EM waves propagating back and forth along the antenna surface. Due to the localized surface plasmon resonance, these waves are accompanied by oscillating free electrons Relative to conventional phase-modulation optical elements, metasurfaces (i.e., 2D versions of metamaterials) have shown novel optical phenomena and promising functionalities with more compact platforms and more straightforward fabrication processes. With the ability to generate a spatial phase variation, optical wavefronts can be manipulated into arbitrary shapes at will, enabling new phenomena and integrated ultrathin optical devices to be explored. This review is focused on recent developments regarding phase manipulation of electromagnetic waves with metasurfaces. Starting from their underlying physics for realizing full 2π phase manipulation, an overview of the applica...

Realizing Broadband Transparency via Manipulating the Hybrid Coupling Modes in Metasurfaces for High‐Efficiency Metalens

“…The fabrication process due to the modulation on optical beams requires phase control everywhere across the beam wavefront. Metasurface is a special class of planar metamaterials, provides enormous degree of freedom to arbitrarily control the wavefront of light beams with locally tailored scattering phase, amplitude, and polarization states using subwavelength macro/nanoparticles . Own to the powerful wave manipulation abilities and planar characteristics, metasurface possesses special advantages compared with traditional optical devices, such as low profile, easy fabrication, and integration.…”

Spin-Orbit Angular Momentum Conversion in Metamaterials and Metasurfaces

“…It is well known that, besides linear momentum, electromagnetic (EM) waves possess angular momentum (AM) [1,2,3,4,5], which can be decomposed into spin angular momentum (SAM) and orbital angular momentum (OAM). Circularly polarized waves carry SAM, quantized as ± per photon for left-hand circular (LHC) and righthand circular (RHC) polarization, respectively.…”

“…Different l-values correspond to mutually orthogonal OAM modes and the total numberof OAM modes is unbounded. OAM modes have been used to encode information and thus to enhance the channel transmission capacity, via OAM multiplexing and multicasting techniques [1,2]. Optical vortices characterizing OAM beams also find a number of applications in super resolution imaging, optical tweezers, detection the rotation of particles at visible, THz and microwave regions [1, 2, 3, 4, 5, 6, 8, 7, 9, 10, 13, 11, ?, 14, 12, 15, 16, 17, 18, 19, 20, 21, 22, 24, 23].…”

“…2D metamaterials, also known as metasurfaces [2,3,4], is an emerging interdisciplinary field which promotes the of use alternative approaches for light arXiv:1904.02647v2 [physics.optics] 25 Jul 2019 engineering based on subwavelength-thick metasurfaces built upon metaatoms, with spatially varying compositions. They exhibit remarkable properties in maneuvering light at a 2D interphase.…”

“…They exhibit remarkable properties in maneuvering light at a 2D interphase. Metasurfaces can not only achieve the functionalities of the 3D counterparts, such as negative refractive index and invisibility cloaking [8,7] but they can also resolve some of the current limits present in 3D metamaterials, such as dielectric loss or high resistive (ohmic) loss [1,2,3]. In addition, metasurfaces can be easily fabricated via standard nanofabrication approaches, such as electron-beam lithography, processes readily available in the semiconductor industry.…”