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.
We study experimentally second-harmonic generation from arrays of split-ring resonators at oblique incidence and find conditions of more than 30-fold enhancement of the emitted second harmonic with respect to normal incidence. We show that these conditions agree well with a nonlinear Rayleigh-Wood anomaly relation and the existence of a surface lattice resonance at the second harmonic. The existence of a nonlinear surface lattice resonance is theoretically confirmed by extending the coupled dipole approximation to the nonlinear case. We further show that the localized surface plasmon modes that collectively contribute to the surface lattice resonance are inherently dark modes that become highly bright due to the collective interaction.
Collective coherent scattering at the surface of a plasmonic nanoparticle array is shown to induce tunable transparency windows at the localized plasmon band. Broadband phase measurements show that the enhanced transmission is accompanied by a large anomalous dispersion, which leads to a group delay as large as within only 40 nm thick sample. This effect occurs over a wide tunable spectral range of , and appears for two distinct counter‐propagating surface waves. The experimental observations are in good agreement with calculations based on coupled dipole approximation (CDA) and with finite‐difference time‐domain (FDTD) simulations. This study opens the door for implementation in the fields of sensing, displays, optical buffering, tunable filtering, and nonlinear optics.
Surface lattice resonances (SLRs) on metasurfaces strongly enhance the interaction of light with the metasurface and can be used for obtaining very high-Q response, high spectral sensitivity, and strong optical nonlinearities. Here, we study experimentally and numerically the dynamic switching of SLRs in gold nanoantenna metasurfaces fabricated on top of indium tin oxide by use of electrically controlled liquid crystals. Experimental results show that the cumulative effects of the anisotropic optical response with an applied electric field and the alignment conditions of liquid crystal molecules significantly affect the formation as well as the strength of SLR modes. We achieve an electrical modulation of >50% in the SLR dips by applying 2 V on the device. The strength of the modulation can be further optimized by modifying the angle of incidence and the polarization of light. These findings demonstrate that plasmonic metasurfaces activated by liquid crystals enable a versatile platform to obtain electro-optical control over SLRs and open the door to various new applications of dynamic reconfigurable metasurfaces.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.