Nonlinear Beam Shaping with Plasmonic Metasurfaces

Abstract

We present here a method for generating second-harmonic beams with tailored beam profiles using nonlinear metasurfaces based on split ring resonators. By manipulating both the phase and the amplitude of the quadratic nonlinear coefficient locally, at the single inclusion level, the emitted second-harmonic wavefront is perfectly controlled. These concepts are demonstrated experimentally by the far-field generation of second-harmonic Airy and vortex beams from nonlinear binary phase computer-generated holograms and the perfect near-field generation of a Hermite–Gauss beam by precise amplitude and phase construction. We believe that these demonstrations open the door to use nonlinear metasurfaces for a variety of integrated nonlinear beam shaping devices.

Advanced control of nonlinear beams with Pancharatnam-Berry metasurfaces

“…If such metasurface is illuminated by a linearly polarized wave, the SH radiation will be shaped into helical beams, and opposite polarizations will be steered in opposite side of the z-axis. Similar responses have been successfully observed in the past using the quasi-periodic polling technique [10,44], which enforces substantial constraints on the size of the beam because the illuminated spot necessarily has to cover a large number of polling periods. In contrast, our approach provides a continuous phase shaping from ultrathin nonlinear metasurfaces with giant conversion efficiencies.…”

“…In adds up to the momentum generated by the phase gradient, resulting in a well-known fork-shaped phase profiles [10,44]. Note that this phase profiles can be readily imprinted in the metasurface itself.…”

“…In addition, ultrathin metasurfaces significantly alleviate phase matching constraints, which are of critical importance for efficient nonlinear processes [1,8]. Several attempts have been recently pursued to apply phase control techniques, which have been originally developed in linear optics, to nonlinear systems, aiming to provide a much-needed control over generated fields at subwavelength scales [3,4,[9][10][11]. Such nonlinear systems with wavefront engineering capabilities are paving the way towards a new paradigm in nonlinear optics, based on which advanced functionalities such as pencil beam steering, focusing, generation of vortex beams, holographic imaging, etc., are realized using ultrathin nonlinear metasurfaces, eliminating the need for bulky optical lenses and filters and mitigating the challenges associated with phasematching.…”

Vectorial control of nonlinear emission via chiral butterfly nanoantennas: generation of pure high order nonlinear vortex beams

“…Nonlinear metasurfaces based on second harmonic generation (SHG) in split-ring resonators (SRR) have been recently demonstrated for beam shaping [23], and focusing and beam steering [24,25]. Tuning the properties of the nonlinear emitters is fundamental for shaping the nonlinear beam phase front [26,27].…”

“…For example, it holds for third harmonic generation (THG), but fails for SHG, which can be explained by the nonlinear scattering model [28]. Examples of nonlinear near-field control in nanostructures have recently been reported [23,[28][29][30][31]. The nonlinear emission control is even more challenging in hybrid dielectric/plasmonic nanostructures, since the nonlinear optical generation can take place in the gap of the nanoantenna due to the presence of a nonlinear material, in the nonlinear dielectric surrounding the nanostructure, or in the nanostructure material itself [32].…”