Showing papers by "John B. Pendry published in 2012"
TL;DR: It is found that the dominant limiting factor is not the resistive loss of the metal, but rather the intrinsic nonlocality of its dielectric response, which has implications for the ultimate performance of nanophotonic systems.
Abstract: Metals support surface plasmons at optical wavelengths and have the ability to localize light to subwavelength regions. The field enhancements that occur in these regions set the ultimate limitations on a wide range of nonlinear and quantum optical phenomena. We found that the dominant limiting factor is not the resistive loss of the metal, but rather the intrinsic nonlocality of its dielectric response. A semiclassical model of the electronic response of a metal places strict bounds on the ultimate field enhancement. To demonstrate the accuracy of this model, we studied optical scattering from gold nanoparticles spaced a few angstroms from a gold film. The bounds derived from the models and experiments impose limitations on all nanophotonic systems.
1,037 citations
TL;DR: Recent and ongoing progress in the realm of active, gain-enhanced nanoplasmonic metamaterials are reviewed and the underlying theoretical concepts of the complex interaction between plasmons and gain media are introduced.
Abstract: Metamaterials have a tremendous potential for applications from biophotonics to optical circuits, although progress has been hampered by intrinsic metal losses. This Review discusses the progress in countering such losses through the use of gain media to realize devices such as nanoplasmonic lasers or improved metamaterials for imaging and nonlinear optical applications.
539 citations
TL;DR: The concept of transformation optics that manipulates electric and magnetic field lines, rather than rays, can provide an equally intuitive understanding of subwavelength phenomena; and at the same time can be an exact description at the level of Maxwell’s equations.
Abstract: Our intuitive understanding of light has its foundation in the ray approximation and is intimately connected with our vision. As far as our eyes are concerned, light behaves like a stream of particles. We look inside the wavelength and study the properties of plasmonic structures with dimensions of just a few nanometers, where at a tenth or even a hundredth of the wavelength of visible light the ray picture fails. We review the concept of transformation optics that manipulates electric and magnetic field lines, rather than rays; can provide an equally intuitive understanding of subwavelength phenomena; and at the same time can be an exact description at the level of Maxwell's equations.
320 citations
TL;DR: It is demonstrated that textured closed surfaces, i.e., particles made of perfect electric conductors (PECs), are able to support localized electromagnetic resonances with properties resembling those of localized surface plasmons (LSPs) in the optical regime and a metamaterial approach is presented that captures the basic ingredients of their electromagnetic response.
Abstract: We demonstrate that textured closed surfaces, i.e., particles made of perfect electric conductors (PECs), are able to support localized electromagnetic resonances with properties resembling those of localized surface plasmons (LSPs) in the optical regime. Because of their similar behavior, we name these types of resonances as spoof LSPs. As a way of example, we show the existence of spoof LSPs in periodically textured PEC cylinders and the almost perfect analogy to optical plasmonics. We also present a metamaterial approach that captures the basic ingredients of their electromagnetic response.
273 citations
TL;DR: An insightful transformation-optics approach is developed to investigate the impact that nonlocality has on the optical properties of plasmonic nanostructures and elucidate the optimum size that maximizes its absorption and field enhancement capabilities.
Abstract: We develop an insightful transformation-optics approach to investigate the impact that nonlocality has on the optical properties of plasmonic nanostructures. The light-harvesting performance of a dimer of touching nanowires is studied by using the hydrodynamical Drude model, which reveals nonlocal resonances not predicted by previous local calculations. Our method clarifies the interplay between radiative and nonlocal effects in this nanoparticle configuration, which enables us to elucidate the optimum size that maximizes its absorption and field enhancement capabilities.
212 citations
TL;DR: In this paper, the effect of plasmonic modes in nanometric Au particle-on-film gaps is investigated experimentally using single-particle dark-field spectroscopy.
Abstract: Polarization-controlled excitation of plasmonic modes in nanometric Au particle-on-film gaps is investigated experimentally using single-particle dark-field spectroscopy. Two distinct geometries are explored: nanospheres on top of and inserted in a thin gold film. Numerical simulations reveal that the three resonances arising in the scattering spectra measured for particles on top of a film originate from highly confined gap modes at the interface. These modes feature different azimuthal characteristics, which are consistent with recent theoretical transformation optics studies. On the other hand, the scattering maxima of embedded particles are linked to dipolar modes having different orientations and damping rates. Finally, the radiation properties of the particle–film gap modes are studied through the mapping of the scattered power within different solid angle ranges.
176 citations
TL;DR: It is shown that, although spatial dispersion reduces the field enhancement taking place at the structure apex, it also diminishes the impact that geometric imperfections have on its performance.
Abstract: The nanofocusing performance of plasmonic tips is studied analytically and numerically. The effects of electron-electron interactions in the dielectric response of the metal are taken into account through the implementation of a nonlocal, spatially dispersive, hydrodynamic permittivity. We demonstrate that spatial dispersion only slightly modifies the device parameters which maximize its field enhancement capabilities. The interplay between nonlocality, tip bluntness, and surface roughness is explored. We show that, although spatial dispersion reduces the field enhancement taking place at the structure apex, it also diminishes the impact that geometric imperfections have on its performance.
131 citations
TL;DR: At zero temperature, the frictional forces due to quantum fluctuations acting on a small sphere rotating near a surface are found to be several orders of magnitude larger than that for the sphere rotating in vacuum.
Abstract: We investigate the frictional forces due to quantum fluctuations acting on a small sphere rotating near a surface. At zero temperature, we find the frictional force near a surface to be several orders of magnitude larger than that for the sphere rotating in vacuum. For metallic materials with typical conductivity, quantum friction is maximized by matching the frequency of rotation with the conductivity. Materials with poor conductivity are favored to obtain large quantum frictions. For semiconductor materials that are able to support surface plasmon polaritons, quantum friction can be further enhanced by several orders of magnitude due to the excitation of surface plasmon polaritons.
108 citations
TL;DR: An analytical approach is proposed, based on transformation optics, to investigate a general class of plasmonic nanostructures with blunt edges or corners, and results evidence the possibility of designing broadband light harvesting devices with an absorption property insensitive to the geometry bluntness.
Abstract: Metallic structures with sharp corners harvest the energy of incident light through plasmonic resonances, concentrating it in the corners and greatly increasing the local energy density. Despite its wide array of applications, this effect is normally strongly dependent on how sharp the corners are, presenting problems for fabrication. In this Letter, an analytical approach is proposed, based on transformation optics, to investigate a general class of plasmonic nanostructures with blunt edges or corners. Comprehensive discussions are provided on how the geometry affects the local field enhancement as well as the frequency and energy of each plasmonic resonance. Remarkably, our results evidence the possibility of designing broadband light harvesting devices with an absorption property insensitive to the geometry bluntness.
92 citations
TL;DR: The excitation of Fano-like resonances in composite nanoparticles has been shown to be useful for controlling their optical properties within an extremely narrow frequency window and transformation optics (TO) has recently been proposed as a route to transfer the broad bandwidth behavior of plasmonic waveguides to nanoantennas using geometric singularities.
Abstract: The spectral characteristics of localized surface plasmons (LSPs) depend strongly on the geometry of the metal nanostructure sustaining them. [ 1 , 2 ] This fact makes the tuning of their lightharvesting and focusing abilities across the whole visible and infra-red regimes possible. Lately, the tailoring of the spectral width of LSP resonances through design has attracted much attention due to its many potential applications in technological areas as diverse as sensing, imaging and photovoltaics. [ 3 , 4 ] The excitation of Fano-like resonances in composite nanoparticles has been shown to be useful for controlling their optical properties within an extremely narrow frequency window. [ 5 ] In contrast, transformation optics (TO) has recently been proposed as a route to transfer the broad bandwidth behavior of plasmonic waveguides to nanoantennas using geometric singularities. [ 6 , 7 ]
60 citations
TL;DR: In this paper, the Leverhulme Trust, the Engineering and Physical Sciences Research Council (EPSRC), and the European Research Council contract No. 290981 PLASMONANOQUANTA (Contract No.
Abstract: This work was supported by the Leverhulme Trust, the Engineering and Physical Sciences Research Council (EPSRC), and the European Research Council (Contract No. 290981 PLASMONANOQUANTA)
TL;DR: The theoretical findings reveal an underlying relation between structural bluntness and spatial dispersion in this particular nanoparticle configuration, and provide analytical and numerical insights into the sensitivity of the device to radiative losses and nonlocal effects.
Abstract: The optical properties of three-dimensional crescent-shaped gold nanoparticles are studied using a transformation optics methodology. The polarization insensitive, highly efficient, and tunable light harvesting ability of singular nanocrescents is demonstrated. We extend our approach to more realistic blunt nanostructures, showing the robustness of their plasmonic performance against geometric imperfections. Finally, we provide analytical and numerical insights into the sensitivity of the device to radiative losses and nonlocal effects. Our theoretical findings reveal an underlying relation between structural bluntness and spatial dispersion in this particular nanoparticle configuration.
TL;DR: The theory of transformation optics is deployed to analytically investigate a variety of blunt plasmonic structures, including overlapping nanowire dimers and crescent-shaped nanocylinders, to support several discrete optical modes, whose energy and line width can be controlled by tuning the nanoparticle geometry.
Abstract: The sharpness of corners/edges can have a large effect on the optical responses of metallic nanostructures. Here we deploy the theory of transformation optics to analytically investigate a variety of blunt plasmonic structures, including overlapping nanowire dimers and crescent-shaped nanocylinders. These systems are shown to support several discrete optical modes, whose energy and line width can be controlled by tuning the nanoparticle geometry. In particular, the necessary conditions are highlighted respectively for the broadband light absorption effect and the invisibility dips that appear in the radiative spectrum. More detailed discussions are provided especially with respect to the structures with asymmetric edge rounding. These structures can support additional subradiant modes, whose interference with the neighboring dipolar modes results in a rapid change of the scattering cross-section, similar to the phenomenon observed in plasmonic Fano resonances. Finite element numerical calculations are als...
TL;DR: It is shown that metal nanoparticles can be used to improve the performance of super-resolution fluorescence nanoscopes based on stimulated-emission-depletion (STED) and lead to a significant expansion of the understanding of biological and biochemical phenomena occurring on the nanoscale.
Abstract: We show that metal nanoparticles can be used to improve the performance of super-resolution fluorescence nanoscopes based on stimulated-emission-depletion (STED). Compared with a standard STED nanoscope, we show theoretically a resolution improvement by more than an order of magnitude, or equivalently, depletion intensity reductions by more than 2 orders of magnitude and an even stronger photostabilization. Our scheme may allow improvement of existing STED nanoscopes and assist in the development of low-power, low-cost nanoscopes. This has the potential to increase the availability of STED nanoscopes and lead to a significant expansion of our understanding of biological and biochemical phenomena occurring on the nanoscale.
TL;DR: In this article, an insightful theoretical description of the optical properties of touching metal nanospheres is presented, which exploits transformation optics ideas within the quasistatic approximation, yields simple expressions for all the relevant electromagnetic magnitudes in these singular nanoparticle geometries.
Abstract: We present an insightful theoretical description of the optical properties of touching metal nanospheres. Our approach, which exploits transformation optics ideas within the quasistatic approximation, yields simple expressions for all the relevant electromagnetic magnitudes in these singular nanoparticle geometries. We demonstrate the highly efficient collection and concentration of light featured by nanosphere dimers, and show the prominent field enhancement that takes place at the point of contact between a single nanoparticle and a flat metal surface. Our method evidences that surface plasmon modes play a key role in the broadband light harvesting capabilities of these nanostructures. The range of validity of our analytical results are explored through the comparison with numerical full electrodynamic simulations.
Patent•
22 Mar 2012
TL;DR: In this paper, a direct-viewing optical device can include customized adjustments that accommodate various optical aberrations of a current user to produce a specified change in optical wavefront at an exit pupil.
Abstract: Exemplary embodiments enable an enhanced direct-viewing optical device to include customized adjustments that accommodate various optical aberrations of a current user. Customized optical elements associated with an authorized current user are incorporated with the direct-viewing optical device to produce a specified change in optical wavefront at an exit pupil. Possible replacement optical elements may have refractive and/or reflective and/or diffractive and/or transmissive characteristics based on current performance viewing factors for a given field of view of the direct-viewing optical device. Some embodiments enable dynamic repositioning and/or transformation of replaceable corrective optical elements responsive to a detected shift of a tracked gaze direction of a current user. Replaceable interchangeable corrective optical elements may be fabricated for current usage or retained in inventory for possible future usage in designated direct-viewing optical devices.
Patent•
29 Feb 2012
TL;DR: In this paper, a real-time adjustment of transformable optical elements is sometimes based on predetermined corrective optical parameters associated with a current user, such as a specified change in optical wavefront at an exit pupil.
Abstract: Exemplary methods, systems and components enable an enhanced direct-viewing optical device to include customized adjustments that accommodate various optical aberrations of a current user. A real-time adjustment of transformable optical elements is sometimes based on predetermined corrective optical parameters associated with a current user. Customized optical elements are incorporated with the direct-viewing optical device to produce a specified change in optical wavefront at an exit pupil. Possible transformable or replacement optical elements may have refractive and/or reflective and/or diffractive and/or transmissive characteristics that are selected based on current performance viewing factors for a given field of view of the direct-viewing device. Some embodiments enable dynamic repositioning and/or transformation of corrective optical elements responsive to a detected shift of a tracked gaze direction of a current user. Replacement corrective optical elements may be fabricated for current usage or retained in inventory for possible future usage in the direct-viewing device.
Patent•
29 Feb 2012
TL;DR: In this article, a real-time adjustment of transformable optical elements is sometimes based on predetermined corrective optical parameters associated with a current user, such as a specified change in optical wavefront at an exit pupil.
Abstract: Exemplary methods, systems and components enable an enhanced direct-viewing optical device to include customized adjustments that accommodate various optical aberrations of a current user. A real-time adjustment of transformable optical elements is sometimes based on predetermined corrective optical parameters associated with a current user. Customized optical elements are incorporated with the direct-viewing optical device to produce a specified change in optical wavefront at an exit pupil. Possible transformable or replacement optical elements may have refractive and/or reflective and/or diffractive and/or transmissive characteristics that are selected based on current performance viewing factors for a given field of view of the direct-viewing device. Some embodiments enable dynamic repositioning and/or transformation of corrective optical elements responsive to a detected shift of a tracked gaze direction of a current user. Replacement corrective optical elements may be fabricated for current usage or retained in inventory for possible future usage in the direct-viewing device.