Airy Beam Generation: Approaching Ideal Efficiency and Ultra Wideband with Reflective and Transmissive Metasurfaces

Abstract

self-healing, and accelerating [3-9] properties. Airy beams are described by light waves that do not diffract, and have shapepreserving features along continuous curved trajectories formed by the peak intensity when the waves propagate in free-space. Numerous studies have demonstrated that Airy beams have great potential for use in many applications such as particle manipulation, [3,4] highresolution light-sheet microscopy, [5] and light bullet generation. [6,7] Traditional ways to produce Airy beams rely on the use of phase masks formed by spatial light modulators, or diffractive optical elements and an extra Fourier-transform lens. [8,9] Such methods are bulky, and not compatible with on-chip integration of nanophotonic systems. Moreover, the pixel sizes of these methods are typically larger than the operation wavelengths, limiting the performance and accuracy. Therefore, generating high-performance Airy beams with subwavelength pixel size, compact footprint, and low cost is challenging, but of great importance for compact and integrated systems. Metasurfaces are planar versions of metamaterials, and have shown unprecedented ability to arbitrarily manipulate light wavefronts, [10-17] providing efficient solutions to generate desired accelerating beams. Metasurfaces are composed of subwavelength-scale dielectric or metallic building blocks that alleviate some challenges of bulky metamaterials, such as volumetric loss, fabrication requirements, and compatibility with on-chip photonic devices. By locally tailoring the amplitude, polarization, and phase of light, recent studies have demonstrated various uses of metasurfaces in many practical applications, including beam shapers, [18,19] focusing lenses, [20,21] multifunctional devices, [22,23] invisibility cloaks, [24,25] etc. In particular, metasurfaces can achieve simultaneous phase and amplitude modulations by absorbing, reflecting, or polarizationconverting the unwanted amplitude components, while using geometric rotating or scaling operations to obtain the desired phase response. [26-29] Based on these metasurfaces, free-space Airy beam generation has been successfully realized with the metasurfaces implemented as orthogonal gold nanorods, [30] C-aperture arrays, [31] etc. However, such techniques have low efficiency and limited bandwidth. To circumvent the high

Stereo Meta‐Atom Enabled Phase–Amplitude Gradient Metasurface for Circularly Polarized Waves

“…[14][15][16] It paves the way to a series of interesting applications, [17,18] and various extension structures are proposed to realize full complex-amplitude modulation. [19][20][21][22][23][24] Though most of the studies about the amplitude and phase regulation of metasurfaces are of linearly polarized waves, some recent studies work on decoupling the A-P for circular polarization (CP) waves, such as by dual geometric phases, [25] dual-phase hybrid, [26] and lossy components [27] in microwaves, and tuning the angle of X-shaped meta-atom [28] and adjusting the thickness of meta-atom [29] in the optical regime. However, the approaches are hindered in the microwave regime because of low efficiency or the limited design freedom.…”

Cubic-Phase Metasurface for Three-Dimensional Optical Manipulation

“…Alternatively, geometric phase methods [ 48 ] (also known as Pancharatnam–Berry phase methods) may be applied to provide additional phase compensation to arrange different rotation angles for each unit cell. Although it can relax the problem of inadequate phase modulation, the geometric phase-based metasurfaces only operate under certain polarization states of incident light [ 47 , 49 , 50 , 51 , 52 , 53 ].…”

Filter-Assisted Metasurface for Full-Space Wavefront Manipulation and Energy Allocation

“…Metasurfaces, − a kind of two-dimensional (2D) analogue of metamaterials, have attracted considerable attention owing to their ability to artificially achieve unique electromagnetic (EM) characteristics over a subwavelength thickness. A diverse assortment of metasurface-based devices, such as planar lenses, , vortex beam generators, − invisibility cloaks, − and information encryptors, , have been implemented by manipulating the amplitude, phase, wavelength, and even spin of EM waves. , Most metasurfaces show their abilities of wave modulations in either the front (reflection) or back (transmission) half-space. Recently, several methods were proposed to realize full-space manipulation of both transmission and reflection waves by multiplexing polarizations − or frequencies, − which multiplies the number of channels on the metasurface in terms of propagation space for modulated waves.…”