Manipulation of Airy surface plasmon beams

Plasmonic Metalens to Generate an Airy Beam

Airy beams represent an important type of non-diffracting beams-they are the only non-diffracting wave in one dimension, and thus they can be produced with a cylindrical geometry that modifies a wavefront in one dimension. In this paper, we show the design of a cylindrical plasmonic metalens consisting of an array of nanoslits in a gold thin layer that modulates the phase of a Gaussian beam to generate an airy beam propagating in free space. Based on the numerical results, we show that it is possible to generate an airy beam by only matching the phase of wavefronts coming out from the array of gold nanoslits to the airy beam phase at plane z=0. We numerically demonstrate that the airy beam exhibits bending over propagation and self-healing properties. The transmission efficiency is around 60%. The simplicity of the proposed structure open new perspectives in the design of flat metasurfaces for light-focusing applications.

Scattering analysis of two-dimensional Airy beams by typical non-spherical particles

The scattering of structured light beams by various particles is an important subject of research with myriad practical applications, such as the manipulation, measurement, and diagnosis of small particles. We carry out an analysis of the scattering of two-dimensional (2D) Airy beams by typical non-spherical particles. The electric and magnetic field vectors of the incident Airy beams are derived by introducing a vector potential in the Lorenz gauge. The scattered fields of the particles are obtained by utilizing the method of moments based on surface integral equations. Some numerical simulations for the scattering of 2D Airy beams by several selected non-spherical particles are performed and analyzed. Especially, a spheroidal particle is taken as an example, and the effects of various parameters describing the 2D Airy beams on its differential scattering cross section are examined. It is expected that this work will be helpful for understanding the interactions of 2D Airy beams with non-spherical particles and their further applications.

Vector wave analysis of Airy beams upon reflection and refraction

As a kind of typical self-accelerating laser beam, Airy beams have attracted much attention due to their fascinating properties and various potential applications. In this work, we carry out a full vector wave analysis of Airy beams upon reflection and refraction. A hybrid method based on the angular spectrum representation and vector potential in the Lorenz gauge is introduced to describe the vectorial structure of Airy beams upon reflection and refraction. The explicit analytical expressions for the electric and magnetic field components of arbitrarily incident Airy beams reflected and refracted at an air-medium interface are derived in detail. Local-field patterns and magnitude profiles with different parameters are displayed. The analytical formulas obtained in this work can be practically applied to explore the local dynamical characteristics, including the energy, momentum, spin, and orbital angular momentum of Airy beams upon reflection and refraction.

Amplitude and Phase of Wave Packets in a Linear Potential

We theoretically study and successfully observe the evolution of Gaussian and Airy surface gravity water wave packets propagating in an effective linear potential. This potential results from a homogeneous and time-dependent flow created by a computer-controlled water pump. For both wave packets we measure the amplitudes and the cubic phases appearing due to the linear potential. Furthermore, we demonstrate that the self-acceleration of the Airy surface gravity water wave packets can be completely canceled by a linear potential.

Polarization-controlled generation of Airy plasmons

Plasmonic metasurfaces have shown great potential to generate Airy plasmons on a metal surface, but the building block of metasurfaces in these works is purposely designed to operate under limited polarization states for the incident light. Here, it is shown that paired nanoslit resonators on a metal surface can provide Airy phase distributions under different polarization incidences. We demonstrate that Airy plasmons can be generated under x-, y-, left-handed circular, and right-handed circular polarization incidences by adjusting the orientation angles of the paired nanoslit resonators. Analogous to previous proposals, Airy plasmons exhibit remarkable non-diffraction, self-healing, and autofocusing properties in the present configuration. The presented design scheme suggests promising applications in polarization-controlled plasmonic circuits and surface optical manipulation.

Simultaneous Airy beam generation for both surface plasmon polaritons and transmitted wave based on metasurface

Based on the amplitude and phase modulation of subwavelength slits, a metasurface which can simultaneously generate Airy beam for surface plasmon polaritons (SPPs) and transmitted wave is presented. Interestingly, by changing the handedness of circularly polarized light, the position of SPPs Airy beam can be switched to the left or right side of the metasurface, while the field distribution and the position of the Airy beam for transmitted wave are not affected. The nondiffracting, self-bending and self-healing properties of the generated Airy beams are analyzed as well. In addition, abruptly autofocusing of SPPs and transmitted wave are demonstrated by interfering two Airy beams. The dual functionality and chirality features of the metasurface can provide more freedoms in the potential applications of Airy beams.

Transverse Anderson localization of surface plasmon polaritons

We investigate the effect of disorder on the propagation of surface plasmon polaritons in arrays of evanescently coupled dielectric loaded surface plasmon polariton waveguides. Diagonal disorder is implemented by randomly varying the heights of the waveguides. Real-space as well as momentum-space images of the surface plasmon polariton intensity distribution in the waveguide arrays are recorded by leakage radiation microscopy. In real space, increasing disorder results in a transverse localization of surface plasmon polaritons. In the momentum distribution, we observe for the first time a disorder-induced transition from a continuous band to a set of discrete modes.

Propagation dynamics of generalized and symmetric Airy beams

We present theoretically and experimentally generalized and symmetric Airy beams, where the two sidelobes are not mutually perpendicular, by introducing two rotary angle factors. The symmetric Airy beam is induced by a binary phase pattern. We demonstrate that the intensity distributions of generalized Airy beams are apparently different from those of normal Airy beams. Moreover, they can propagate along arbitrary trajectories. Numerical results show that the generalized and symmetric Airy beams still have the ability of self-healing and nondiffraction. The experimental results are in complete accord with numerical results. Some possible applications are also discussed, and these interesting properties will also likely have potential applications.

Hybrid Airy plasmons with dynamically steerable trajectories

With their intriguing diffraction-free, self-accelerating, and self-healing properties, Airy plasmons show promise for use in the trapping, transporting, and sorting of micro-objects, imaging, and chip scale signal processing. However, high dissipative loss and lack of dynamical steerability restrict the implementation of Airy plasmons in these applications. Here we reveal hybrid Airy plasmons for the first time by taking a hybrid graphene-based plasmonic waveguide in the terahertz (THz) domain as an example. Due to coupling between optical modes and plasmonic modes, the hybrid Airy plasmons can have large propagation lengths and effective transverse deflections, where the transverse waveguide confinements are governed by the hybrid modes with moderate quality factors. Meanwhile, the propagation trajectories of the hybrid Airy plasmons are dynamically steerable by changing the chemical potential of graphene. These hybrid Airy plasmons may promote the further discovery of non-diffracting beams along with the emerging developments of optical tweezers and tractor beams.

Quasi-Airy beams along tunable propagation trajectories and directions

We present a theoretical and experimental exhibit that accelerates quasi-Airy beams propagating along arbitrarily appointed parabolic trajectories and directions in free space. We also demonstrate that such quasi-Airy beams can be generated by a tunable phase pattern, where two disturbance factors are introduced. The topological structures of quasi-Airy beams are readily manipulated with tunable phase patterns. Quasi-Airy beams still possess the characteristics of non-diffraction, self-healing to some extent, although they are not the solutions for paraxial wave equation. The experiments show the results are consistent with theoretical predictions. It is believed that the property of propagation along arbitrarily desired parabolic trajectories will provide a broad application in trapping atom and living cell manipulation.

Lossless Airy Surface Polaritons in a Metamaterial via Active Raman Gain

We propose a scheme to realize a lossless propagation of linear and nonlinear Airy surface polaritons (SPs) via active Raman gain (ARG). The system we suggest is a planar interface superposed by a negative index metamaterial (NIMM) and a dielectric, where three-level quantum emitters are doped. By using the ARG from the quantum emitters and the destructive interference effect between the electric and magnetic responses from the NIMM, we show that not only the Ohmic loss of the NIMM but also the light absorption of the quantum emitters can be completely eliminated. As a result, non-diffractive Airy SPs may propagate for very long distance without attenuation. We also show that the Kerr nonlinearity of the system can be largely enhanced due to the introduction of the quantum emitters and hence lossless Airy surface polaritonic solitons with very low power can be generated in the system.

Propagation characteristics of continuously tuning distorted Airy-like beams

We investigate theoretically and observe experimentally a continuously tuning distorted Airy-like beam, which is generated by introducing a controllable rotation angle into the phase patterns. The beam wavefront can be tuned flexibly by using the introduced angle. The main lobes of beams can be controlled readily to propagate along specified parabolic trajectories. The relevant optical behaviors are discussed and demonstrated in detail. The experimental results are in good agreement with the theoretical analysis. The intriguing characteristics of the continuously tuning Airy-like beams could provide more degrees of freedom in cell and atom manipulation.

Comprehensive imaging of terahertz surface plasmon polaritons

A comprehensive system with a high speed is built for imaging the terahertz (THz) surface plasmon polaritons (SPPs). Both the amplitude and the phase information of the focusing THz-SPPs excited by a semicircular plasmonic lens are achieved by using this system. The amplitude images present the focusing profiles of the THz-SPPs with different frequencies and the phase images reveal the Gouy phase shift as the THz-SPPs evolving through the focus. The simulations are also performed and a good agreement between the experimental and simulated results has been found.

Bloch oscillations in plasmonic waveguide arrays

The combination of modern nanofabrication techniques and advanced computational tools has opened unprecedented opportunities to mold the flow of light. In particular, discrete photonic structures can be designed such that the resulting light dynamics mimics quantum mechanical condensed matter phenomena. By mapping the time-dependent probability distribution of an electronic wave packet to the spatial light intensity distribution in the corresponding photonic structure, the quantum mechanical evolution can be visualized directly in a coherent, yet classical wave environment. On the basis of this approach, several groups have recently observed discrete diffraction, Bloch oscillations and Zener tunnelling in different dielectric structures. Here we report the experimental observation of discrete diffraction and Bloch oscillations of surface plasmon polaritons in evanescently coupled plasmonic waveguide arrays. The effective external potential is tailored by introducing an appropriate transverse index gradient during nanofabrication of the arrays. Our experimental results are in excellent agreement with numerical calculations.