Plasmonic metasurfaces represent a promising platform for enhancing light-matter interaction. Active control of the optical response of metasurfaces is desirable for applications such as beam-steering, modulators and switches, biochemical sensors, and compact optoelectronic devices.Here we use a plasmonic metasurface with two Fano resonances to enhance the interaction of infrared light with electrically controllable single layer graphene. It is experimentally shown that the narrow spectral width of these resonances, combined with strong light/graphene coupling, enables reflectivity modulation by nearly an order of magnitude leading to a modulation depth as large as 90%. . Numerical simulations demonstrate the possibility of strong active modulation of the phase of the reflected light while keeping the reflectivity nearly constant, thereby paving the way to tunable infrared lensing and beam steering.
We show that two-dimensional arrays of thin metallic wires can guide transverse electromagnetic (TEM) waves and focus them to the spatial dimensions much smaller that the vacuum wavelength. This guiding property is retained for the tapered wire bundles which can be used as multichannel TEM endoscopes: they capture a detailed electromagnetic field profile created by deeply sub-wavelength features of the studied sample and magnify it for observation. The resulting imaging method is superior to the conventional scanning microscopy because of the parallel nature of the image acquisition by multiple metal wires. Possible applications include terahertz and mid-infrared endoscopy with nanoscale resolution. PACS numbers:Diffraction of light is the major obstacle to a variety of applications requiring concentrating optical energy in a small spatial volume: light cannot be confined to dimensions much smaller than half of its wavelength λ/2. Applications that would benefit from overcoming the diffraction limit include nonlinear spectroscopy and harmonics generation [1,2,3,4], sub-wavelength optical waveguiding [5,6,7], and nanofabrication [8]. Utilizing plasmonic materials with a negative dielectric permittivity circumvents diffraction limit because interfaces between polaritonic (ǫ < 0) and dielectric (ǫ > 0) materials support surface plasmons that can be confined to sub-λ dimensions. Examples of diffraction-beating devices based on plasmonics include superlenses [9,10,11,12], coupled-sphere waveguides [13], and sharp focusing tips [14].High losses associated with surface plasmonics are hampering many of these applications.Another challenge yet to be met is designing practical imaging modalities based on sub-λ plasmons that convert near-field electromagnetic (EM) perturbations into the far field where they can be easily observed. In this Letter we propose a solution to these two problems: a tapered multi-wire array supporting sub-wavelength transverse electromagnetic (TEM) waves. Examples of the multi-wire endoscopes based on such arrays (un-tapered and tapered) are shown in Fig. 1. We have demonstrated that the tapered endoscope can accomplish two tasks: (i) creating near the base of an endoscope a magnified image of deeply sub-wavelength objects (metal spheres, in our case) placed at the endoscope's tip [see Fig. 3(a)], and (ii) creating near the tip of an endoscope a de-magnified image of a mask placed at the endoscope's base [see Fig. 3(b)]. Accomplishing the first task is necessary for making a sub-λ sensor while accomplishing the second one -for making a sub-λ lithographic tool.Single metallic wires and coaxial wire cones have recently attracted considerable attention as low-loss waveguides [15,16] of TEM-like modes of THz and far-infrared radiation. Using a single wire waveguide has its limitations: for example, if a wire is used as a high spatial resolution sensor, then only a single bit of information can be collected without scanning the wire. We demonstrate that a bundle of closely spaced wires can act as a mul...
Abstract:Plasmonic metasurfaces are able to modify the wavefront by altering the light intensity, phase and polarization state. Active plasmonic metasurfaces would allow dynamic modulation of the wavefront which give rise to interesting application such as beam-steering, holograms and tunable waveplates. Graphene is an interesting material with dynamic property which can be controlled by electrical gating at an ultra-fast speed. We use a graphene-integrated metasurface to induce a tunable phase change to the wavefront. The metasurface supports a Fano resonance which produces high-quality resonances around 7.7 microns. The phase change is measured using a Michleson interferometry setup. It is shown that the reflection phase can change up to 55 degrees. In particular the phase can change by 28 while the amplitude is nearly constant. The anisotropic optical response of the metasurface is used to modulate the ellipticity of the reflected wave in response to an incident field at . We show a proof of concept application of our system in potentially ultra-fast laser interferometry with sub-micron accuracy.Introduction:
Highly compact, filter-free multispectral photodetectors have important applications in biological imaging, face recognition, and remote sensing. In this work, we demonstrate room-temperature wavelength-selective multipixel photodetectors based on GaAs 0.94 Sb 0.06 nanowire arrays grown by metalorganic vapor phase epitaxy, providing more than 10 light detection channels covering both visible and near-infrared ranges without using any optical filters. The nanowire array geometry-related tunable spectral photoresponse has been demonstrated both theoretically and experimentally and shown to be originated from the strong and tunable resonance modes that are supported in the GaAsSb array nanowires. High responsivity and detectivity (up to 44.9 A/W and 1.2 × 10 12 cm √Hz/W at 1 V, respectively) were obtained from the array photodetectors, enabling highresolution RGB color imaging by applying such a nanowire array based single pixel imager. The results indicate that our filter-free wavelength-selective GaAsSb nanowire array photodetectors are promising candidates for the development of future high-quality multispectral imagers.
An active negative index metamaterial that derives its gain from an electron beam is introduced. The metamaterial consists of a stack of equidistant parallel metal plates perforated by a periodic array of holes shaped as complementary split-ring resonators. It is shown that this structure supports a negative-index transverse magnetic electromagnetic mode that can resonantly interact with a relativistic electron beam. Such metamaterial can be used as a coherent radiation source or a particle accelerator.
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.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.