Ultra‐Broadband High‐Efficiency Airy Optical Beams Generated with All‐Silicon Metasurfaces

Abstract

a wide range of applications including optical micromanipulation, [1,2] chip-scaled signal processing, [3,4] microscopy, [5,6] generation of curved plasma channels, [7] light bullet, [8,9] and vacuum electron acceleration. [10,11] For generating Airy optical beams, it is highly desirable to precisely control light waves to satisfy the amplitude and phase distributions described by Airy function. Conventional protocols for generating Airy beams rely on the utilization of bulky optical elements, such as spatial light modulators (SLMs), [5,9,12,13] liquid crystals (LCs), [14-16] lens, [17] and phase plate. [18,19] These schemes suffer from low transmission efficiencies with SLMs or LCs (typically less than 40%), and long device lengths with lens and phase plates. [16-20] Metasurfaces provide an unprecedented approach to control light waves in terms of amplitude, phase, polarization, and so on. The past few years have witnessed the rapid development of optical functional devices and applications with metasurfaces, including polarization control, [21-24] flat lens, [25-30] holographic imaging, [31-33] invisibility cloaks, [34,35] and orbital angular momentum. [36-39] Different from phase-only modulation optical elements and applications, such as lens or holograms, the implementation of Airy beams requires simultaneous amplitude and phase modulation. Recently, metasurfaces offered a compact method to build Airy beam generators due to their great capability to manipulate light waves. Many metasurface configurations, including plasmonic metasurfaces, [40-45] dielectric nano-rods, [46-48] and hyperbolic metamaterials [49] have been developed for Airy beam generation in the past few years. However, most of these schemes use some resonant building blocks to modulate light waves across the resonant frequencies; the resultant phase and amplitude profiles no longer abide by the Airy function out of the resonant frequencies. Consequently, the Airy beams can only be realized within a rather narrow bandwidth around the resonant frequencies. Some efforts have been dedicated to broadening the working bandwidth, but the transmission efficiencies are reduced significantly once the working frequencies deviate from the resonant frequencies. [42,45] The recently reported dielectric metasurfaces have provided a robust approach to increase the transmission efficiency, however, these schemes are purposely designed to enable phase modulation, resulting in low quality of the generated beams due to lack of amplitude modulation. [46-48] Broadband high-efficiency Airy beams have been proposed and experimentally demonstrated Conventional approaches for generating Airy beams rely upon bulky and costly systems, which impede the miniaturization of optical systems. Metasurfaces have provided a compact method to generate Airy optical beams, but the current schemes suffer from the issues of narrow bandwidths and/or low transmission efficiencies. Here, a design strategy of constructing broadband and high-efficiency transmissive Airy optical beam genera...

Enhanced Sub‐Terahertz Microscopy based on Broadband Airy Beam

“…It is worth noting that the bandwidth of the generated Airy beam in this work (fractional bandwidth of 20%) is not as wide as some previous works. [ 33,34 ] For the proof‐of‐concept of the ESTM technique based on broadband Airy beam, the presented results can already validate the effectiveness of the new method. It is certainly possible to apply other reported approaches to construct Airy beams with a broader bandwidth and better microscopic image quality may be obtained.…”

Cubic-Phase Metasurface for Three-Dimensional Optical Manipulation

“…A schematic diagram of the metasurface is shown in Figure 1 a. In contrast to a paraxial wave equation of Airy beams [ 25 , 51 ], the phase distribution of the metasurface is calculated based on the principle of geometrical optics [ 47 , 49 ]. One-dimensional trajectory curve, reduced from 2D trajectory plane of accelerating beam with the metasurface positioned on z = 0 plane, is used for simplicity.…”

“…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 ].…”

Direction‐Reversible Accelerated Beam Generation Based on Metasurfaces

“…[26] Ju Z et al utilized the metasurface consisting of silicon pillars to realize ultra-broadband high-efficiency Airy beam. [27] Chen S et al proposed the metasurface composed of orthogonal nanorods to modulate the phase and amplitude of light field and generated plasmonic Airy beam with an ideal deflection trajectory. [28] Examining the above works about the accelerated beams, one can see they have one common characteristic.…”