Generation Of Airy Beams Research Articles

Multichannel Airy beam generator simultaneously for linear and circular polarized waves

The Airy beam has intrigued long-held research interests and developed various striking applications attributed to the unprecedented diffraction-free, self-bending and self-healing properties. Metasurfaces with superior design freedom and small structure size open a fire-new avenue for generating efficient and broadband Airy beam. Nevertheless, most existing Airy beam generators can only respond to one polarization state of electromagnetic waves and produce the single Airy beam, which immensely limit the serviceability and utilization of the Airy beam generators. Herein, an inspiring strategy of multichannel Airy beam generator based on the multichannel amplitude and phase controlled metasurface is proposed to independently generate the Airy beams for linear polarized waves in 20–24 GHz and orthogonal circular polarized waves in 12–14 GHz and 15–17 GHz. Notably, an appealing paradigm of multichannel beam focusing can be realized by the integrated multichannel Airy beam generator, which possesses strong ability to circumvent the obstacle owing to the self-healing feature of the Airy beam. A proof-of-concept prototype is constructed to verify the feasibility of our methodology, and multitudinous simulations and experiments are in excellent accordance with our theoretical predictions. This novel design of multichannel Airy beam generator will have tremendous application potential in sensing, communication and other multifunctional metadevices.

Generation and propagation of Airy beams and 1-inch diameter focusing optics using three-dimensional-printed polymer optics

The additive manufacture of polymer optical elements has the promise of reducing component weight, providing new design capabilities, and enhanced performance for a wide variety of military and commercial optical systems. We review progress in the development of three-dimensional (3D)-printed gradient index (GRIN) lenses and optical phase masks. The 3D printing process uses a modified commercial inkjet printer and ultraviolet curable polymers that have specific nanoparticles added to them to modulate the index of refraction. Complex optical phase masks for the generation of Airy laser beams and polymer GRIN lenses to replace conventional glass lenses used in a telescope or riflescope are created. The generation and propagation of Airy beams using these polymer-generated optical phase masks have been investigated and analyzed through experimentation, simulations, and comparison with recent theoretical predictions. Airy beams have been generated using the conventional approach with a spatial light modulator and compared to the 3D printed optical phase masks. The maximum nondiffracting propagation distance of an aperture truncated Airy beam was experimentally measured. The results show that the maximum nondiffracting propagation distance of a laboratory generated Airy beam is proportional to x02, the Airy beam waist size squared. The size of the Gaussian envelope beam has a weaker effect on the Airy beam propagation distance. The experimental results were compared with current theoretical models. A set of 1-inch-diameter 100-mm focal length polymer GRIN lenses have been made using 3D printing. Transmission and modulation transfer function results for the lenses are reported.

Ultra-wideband two-dimensional Airy beam generation with an amplitude-tailorable metasurface.

Airy beams, accelerating optical beams with exotic properties of self-bending, self-healing and non-diffraction, are essential for a wide range of photonics applications. Recently, metasurfaces have provided an efficient platform for generating desired Airy beams within a thin thickness, but they suffer from the narrow bandwidth, especially for two-dimensional (2D) Airy beams. Here, we propose an amplitude-tailorable polarization-converting metasurface to enable ultra-wideband 2D Airy beam generation. The amplitude and phase profiles for the 2D Airy beam can be realized by tuning only the orientation of the multi-resonant meta-atom, which can operate in the range of 6.6 GHz to 23.7 GHz, or fractional bandwidth of 113%. An exemplary prototype is measured to validate the design principle, which is in agreement with the simulation results. The proposed method holds great promise for wavefront shaping, and may facilitate the uses of Airy beam for practical applications.

Terahertz structured light: nonparaxial Airy imaging using silicon diffractive optics

Structured light – electromagnetic waves with a strong spatial inhomogeneity of amplitude, phase, and polarization – has occupied far-reaching positions in both optical research and applications. Terahertz (THz) waves, due to recent innovations in photonics and nanotechnology, became so robust that it was not only implemented in a wide variety of applications such as communications, spectroscopic analysis, and non-destructive imaging, but also served as a low-cost and easily implementable experimental platform for novel concept illustration. In this work, we show that structured nonparaxial THz light in the form of Airy, Bessel, and Gaussian beams can be generated in a compact way using exclusively silicon diffractive optics prepared by femtosecond laser ablation technology. The accelerating nature of the generated structured light is demonstrated via THz imaging of objects partially obscured by an opaque beam block. Unlike conventional paraxial approaches, when a combination of a lens and a cubic phase (or amplitude) mask creates a nondiffracting Airy beam, we demonstrate simultaneous lensless nonparaxial THz Airy beam generation and its application in imaging system. Images of single objects, imaging with a controllable placed obstacle, and imaging of stacked graphene layers are presented, revealing hence potential of the approach to inspect quality of 2D materials. Structured nonparaxial THz illumination is investigated both theoretically and experimentally with appropriate extensive benchmarks. The structured THz illumination consistently outperforms the conventional one in resolution and contrast, thus opening new frontiers of structured light applications in imaging and inverse scattering problems, as it enables sophisticated estimates of optical properties of the investigated structures.

Zero Acceleration and Non‐Self‐Healing Airy Beam Propagation near a Black Hole

AbstractIn this paper, an analytical expression of Airy beams near a black hole is derived by general relativity concepts. This paper demonstrates the self‐acceleration and the self‐healing properties of Airy beams near a black hole with different Schwarzschild radii. It shows, during transmission, that the equivalent acceleration near a black hole decreases to a minimum negative value, then increases and eventually approaches zero. After propagating a certain distance, the trajectories of Airy beams approaching a black hole may no longer travel along parabolas, but rather almost straight lines due to the existence of the strong gravitational field. The shapes of the wave structure of Airy beams remain unvarying during the transmission, which indicates that the nondiffraction characteristic is still present. Moreover, the self‐healing property of Airy beams near a black hole gradually disappears with the increase of the strength of the gravitational field, because the energy flow to the major lobe is prevented by the gravitational field of the black hole. These intriguing features may open new prospects in the fields of nanophotonic optics, relativistic effects, transformation optics, and so on.

Generation of Airy beams with transmissive cross-polarization conversion metasurfaces

This paper present a 1D finite-energy Airy beam generator at 8.0 GHz using a transmissive metasurface composed of coupling-propagation-decoupling unit cells. The phase and amplitude of the cross-polarized transmitted waves can be controlled by changing the length of the stripline and the position of loaded shorting pins, respectively. Utilizing this property to reshape the field of transmitted waves in accordance with the desired phase and amplitude profile of 1D finite-energy Airy beams. The designed metasurface is fabricated to measure the quasi-nondiffraction and self-bending properties of the generated 1D Airy beams at 8.0 GHz. In addition, the presented Airy beams generator has a very thin thickness of 0.05 (≈2 mm). The measured results were found to be in good agreement with the simulated results. Thanks to the independent control of phase, amplitude and polarization, the designed unit cell can be used in structured light, beam shaping, and holography etc.

Generation of elliptical airy vortex beams based on all-dielectric metasurface

Elliptical airy vortex beams (EAVBs) can spontaneously form easily identifiable topological charge focal spots. They are used for topological charge detection of vortex beams because they have the abruptly autofocusing properties of circular airy vortex beams and exhibit unique propagation characteristics. We study the use of the dynamic phase and Pancharatnam–Berry phase principles for generation and modulation of EAVBs by designing complex-amplitude metasurface and phase-only metasurface, at an operating wavelength of 1500 nm. It is found that the focusing pattern of EAVBs in the autofocusing plane splits into |m|+1 tilted bright spots from the original ring, and the tilted direction is related to the sign of the topological charge number m. Due to the advantages of ultra-thin, ultra-light, and small size of the metasurface, our designed metasurface device has potential applications in improving the channel capacity based on orbital angular momentum communication, information coding, and particle capture compared to spatial light modulation systems that generate EAVBs.

Multiple Airy beam generation by a digital micro mirror device.

The Airy beam is the solution of Maxwell's wave equation and since this equation is linear, a superposition of Airy beams still remains the solution of the wave equation. In this paper, we propose a method for generating multiple Airy beams that includes a desirable number of up to 6 individual Airy beams with desirable acceleration properties. By introducing a decenter into the designed diffractive optical element (DOE) of an Airy beam the problem of generating dual airy beams patterns by an amplitude-based spatial light modulator is solved. By superimposing the designed DOEs of individual Airy beams and scaling them to the proper gray level range, the DOE of the multiple Airy beams is generated. Displaying this DOE on a digital micromirror device, multiple Airy beams are experimentally produced. The experimental studies of these beams show good agreement with the performed simulations.

Generation of Airy beams in Smith-Purcell radiation.

The metasurface has recently emerged as a powerful platform to engineer wave packets of free electron radiation at the mesoscale. Here, we propose that Airy beams can be generated when moving electrons interact with bianisotropic metasurfaces. By changing the intrinsic coupling strength, full amplitude coverage and 0-to-π phase switching of Smith-Purcell radiation can be realized from the meta-atoms. This unusual property shifts the wave front of the assembled Airy beam toward a parabolic trajectory. Experimental implementation displays that evanescent fields bounded at slotted waveguides can be coupled into Airy beams via Smith-Purcell radiation from a designed bianisotropic metasurface. Our method and design strategy offer an alternative route toward free-electron lasers with diffraction-free, self-accelerating, and self-healing beam properties.

Terahertz Airy beam generated by Pancharatnam-Berry phases in guided wave-driven metasurfaces.

Metasurface antennas scatter traveling guided waves into spatial waves, which act as extendable subsources to overcome the size limitation on emission sources. With the use of a Pancharatnam-Berry phase metasurface stimulated by a circularly polarized wave in a waveguide, the local phase distributions of scattered spatial waves can be made consistent with those of an Airy beam, thereby allowing the generation of high-quality Airy beams. In a slab waveguide, circularly polarized waves are synthesized through superposition of in-plane transverse electric modes. Simulations demonstrate that a 20 mm × 20 mm footprint all-dielectric guided wave-driven metasurface generates a 2D Airy beam at a frequency of 0.6 THz. Furthermore, we employ a metasurface deposited on a strip waveguide to generate a 1D Airy beam under direct stimulation by the fundamental transverse electric mode. Our work not only provides a large-scale emitter, but it also suggests promising potential applications in on-chip imaging and holography.

Quasi-bound states in the continuum-based switchable light-field manipulator

Nonlocal metasurfaces, which support a collective mode, can be applied to manipulate the wavefront within the narrow band spectrum and do not operate other wavelengths. However, once fabricated, the tunability of those meta-devices is still a challenge. Here, we demonstrated a switchable all-dielectric nonlocal metasurface based on quasi-bound states in the continuum controlled by symmetry breaking. This device realizes the spatial light beam manipulation in the narrow band with switchable resonant wavelengths in different environment dielectric. We designed a nonlocal metasurface for beam focusing with a tunable wavelength in the communication band. We also designed a nonlocal metasurface for the generation of non-diffraction Airy beams with tunable wavelength. These results will have potential applications in see-through display, large-capacity optical communications, nonlinear optics and imaging.

Generation of achromatic auto-focusing Airy beam for visible light by an all-dielectric metasurface

The focusing performance of optical beams has always played an important role in various applications such as imaging, displaying, and sensing. In contrast to a traditional focused beam with gradually increasing light intensity, an auto-focusing Airy beam exhibits an abrupt way of focusing light energy. However, owning to the chromatic dispersion of light, the previously demonstrated auto-focusing Airy beam always suffers from chromatic aberration. Here, we show that with judicious dispersion engineering of its constituent nanostructures, a metasurface can generate auto-focusing Airy beam without chromatism for the visible light. In experimental demonstration, we implement a dielectric metasurface composed of TiO2 nanopillars that generates an achromatic auto-focusing Airy beam with diffraction-limited performance covering the wavelength range from 450 to 600 nm. This study paves the way toward efficient achromatic auto-focusing Airy beam generation based on flat optical components, enabling diverse potential applications including biomedical imaging, light-sheet microscopy, and particle manipulation.

Propagation and Evolution Properties of Finite Energy Airy Beams

Propagation and Evolution Properties of Finite Energy Airy Beams

Propagation of Vortex Symmetric Airy Beam in the Turbulent Link

Propagation of Vortex Symmetric Airy Beam in the Turbulent Link

Enhanced Sub‐Terahertz Microscopy based on Broadband Airy Beam

AbstractNon‐diffraction electromagnetic beams such as Airy beams attract wide exploration in various disciplines owing to its fascinating features and great potential of applications. Although generation and applications of Airy beams are actively studied in the optical regime, applications of Airy beams in the THz or sub‐THz domain are rarely explored. This work proposes a new microscopic technique leveraging a sub‐THz broadband non‐diffraction Airy beam as the illumination beam to improve the image quality, which is named as enhanced sub‐THz microscopy (ESTM). The effectiveness of the ESTM is validated by a metallic sample, which shows that applying broadband measured information can render a better image quality than only using single‐frequency information. By blocking the sample using a scattering obstacle, it is demonstrated that the self‐reconstruction property of the Airy beam can efficiently suppress the distortion induced by the obstacle and good images can still be obtained. In addition, it is shown that the image quality applying a broadband Airy beam is superior to that of non‐diffraction quasi‐Bessel beams and other conventionally used illumination beams for microscopic technique.

1D Self-Healing Beams in Integrated Silicon Photonics

Since the first experimental observation of optical Airy beams, various applications ranging from particle and cell micromanipulation to laser micromachining have exploited their non-diffracting and accelerating properties. The later discovery that Airy beams can self-heal after being blocked by an obstacle further proved their robustness to propagate under scattering and disordered environment. Here, we report the generation of Airy beams on an integrated silicon photonic chip and demonstrate that the on-chip 1D Airy beams preserve the same properties as the 2D beams. The 1D meta-optics used to create the Airy beam has the size of only 3 by 16 microns, at least three orders of magnitude smaller than the conventional optic. The on-chip self-healing beams demonstrated here could potentially enable diffraction-free light routing for on-chip optical networks and high-precision micromanipulation of bio-molecules on an integrated photonic chip.

Direct Generation of Airy Beams at Designed Fourier Planes Using Integrated Airy Phase Plates

Featuring extraordinarily curved propagation trajectories, self-accelerating Airy beams have stimulated considerable interests from academic research to practical applications. However, generation of high-quality Airy beams using compact optical devices is still highly desirable. Here we present a design of integrated Airy phase plates (IAPPs) with a miniature size (60 μm × 60 μm × 1.1 μm). In addition, a phase-type Fresnel zone plate (FZP) is incorporated in the phase element to further reduce the system dimension, endowing the IAPPs the ability of directly generating Airy beams without introducing a bulky Fourier transform (FT) lens. The fabrication of IAPPs is facilitated by femtosecond direct laser writing (FsDLW), and the experimentally generated Airy beams are in good agreement with the numerical simulations. Furthermore, the flexible fabrication of IAPPs with different focal lengths is demonstrated, which results in the generation of Airy beams at different Fourier planes as desired. Our design strategy and fabrication methodology of the microscale three-dimensional (3D) phase plates can unfold new capacities of Airy beams for miniaturization applications in fiber optics and in on-chip photonics.

Airy beam propagation: autofocusing, quasi-adiffractional propagation, and self-healing.

We study the propagation of superpositions of Airy beams and show that, by adequately choosing the parameters in the superposition, effects as opposite as autofocusing and quasi-adiffractional propagation may be obtained. We also give a simple analytical expression for free propagation of any initial field, based on so-called number states (eigenstates of the quantum harmonic oscillator), that allows us to study their self-healing properties.

High Efficient Metadevices for Terahertz Beam Shaping

Metasurfaces supply a planar approach for flexible wavefront manipulation, thus facilitating the integration and minimization of optical elements, especially in the terahertz (THz) range. High efficient THz metadevices are highly pursued at present. Here, we propose a bilayer design to improve the efficiency of metadevice. Two silicon pillar arrays with distinguishing geometries are integrated on single silicon substrate. On one side, elliptical silicon pillars, with geometry optimized for the target frequency, are spatially orientated to realize the desired Pancharatnam-Berry phase. On the other side, uniform circular silicon pillars are set to suppress the reflection. With this design, versatile metadevices such as lens, lens array, polarization fork grating, Bessel vortex generator, and Airy beam generator are demonstrated. Maximum efficiency up to 95% for the target frequency and excellent design flexibility are verified. It provides a practical strategy for the generation of compact and high-efficiency THz metadevices, which suit for high-performance THz imaging and communication apparatuses.

Broadband Efficient Polarization‐Pure Airy Beam Generation Based on Three‐Layer Metasurface

Herein, a polarization‐pure Airy beam generation strategy based on twisted layer structures, which is broadband with efficiency approaching the theoretical limit, is proposed. As demonstration, an Airy beam generator operating in the microwave regime is built with stacked three‐layer identical complementary split ring resonators (CSRRs) as the unit cell. By spatially arranging the orientation angle of the middle layer in each unit cell, linearly polarized incident waves can be converted to an Airy beam in cross‐polarization, whereas the unmodulated copolarized component is strongly suppressed in the transmitted field. The proposed Airy beam generation strategy along with the transmission amplitude and phase modulation method can be implemented at terahertz and even infrared regimes using various other twisted multilayer structures.