Generating stable tractor beams with dielectric metasurfaces

Abstract

Propagation invariant beams that pull objects towards a light source are commonly known as tractor beams. Here, an efficient linearly polarized tractor beam with improved stability is introduced. The beam consists of a superposition of TE and TM polarized Bessel beams of orders m = +1 and m = −1. It is shown that this beam can stably pull a wide range of dielectric microparticles arbitrarily long distances, independent of ambient conditions. Next, a straightforward method of generating these high performance beams is proposed. A Si metasurface transforms an incident linearly polarized Gaussian beam into the desired tractor beam. Full-wave simulations demonstrate that it is possible for this simple geometry to pull a polystyrene sphere a distance equal to the non-diffracting range of the Bessel beam. The simplicity of the setup and the robust performance of the proposed tractor beam significantly enhance the ability to manipulate matter with light.

Advances in Full Control of Electromagnetic Waves with Metasurfaces

“…Reproduced with permission. [ 158 ] Copyright 2015, APS. c) Cherenkov surface plasmon wakes with one-dimensional metamaterials.…”

“…The proposed Si metasurface was able to convert a normally incident Gaussian beam into a tractor beam over a distance of 5 λ 0 , where λ 0 is the operation wavelength. [ 158 ] The manipulation region can be further enlarged by increasing the diameter of metasurface and Gaussian beam. It opens a remarkable door to generate other structured beams to realize more sophisticated particle manipulations in diverse environments.…”

Design, concepts, and applications of electromagnetic metasurfaces

“…More sophisticated metasurfaces, transforming both phase and polarization, have been recently realized. This includes metasurfaces producing beams possessing angular orbital momentum [57] or vortex waves [58][59][60][61][62][63], holograms [64,65], and stable beam traction [66]. Additionally, nonreciprocal transformations [67][68][69][70][71], nonlinear interactions [72][73][74], analog computing [75,76], and spatial filtering [77][78][79] have also been reported.…”

Formation of high-order acoustic Bessel beams by spiral diffraction gratings

“…The variation of the phase (φ) with the angle (θ ) is therefore increased, and the conical wave front formed by the axisymmetric grating presents a total phase shift of 2πn over a complete turn as follows from Eq. (9). When converging to the axis, the conical wave front forms a Bessel beam in the same way as in the previous section.…”

“…However, it is possible to generate finite size approximations for Bessel beams which propagate over extended distances in a diffraction-free manner providing potential applications for the wave physics community [2][3][4][5][6][7]. Whereas zeroth-order Bessel beams present a bright central maximum and can be useful for applications that require focusing of energy [8], the vortex beams generated by the HOBBs can be useful for manipulating particles in both optics [9] and acoustics [10].…”