Negative refractive index materials (NRIM) make possible unique effects such as a convergent at lens due to the reversed Snell-Descartes laws of refraction. NRIM are also known to be able to support a host of surface plasmon states for both polarizations of light which are responsible for the sub-wavelength image resolution achieved by a slab of NRIM. A generalized lens theorem provides us with a class of spatially varying slab lenses satisfying the prerequisite symmetries to fold the optical space onto itself. This theorem can be derived using powerful tools of transformational optics. A paradigm of such complementary media are checkerboards consisting of alternating cells of positive and negative refractive index that represent a very singular situation in which the local density of modes at the corners are enormously enhanced. We have considered several theoretical and numerical aspects of such structured films including a finite slabs of multi-scale checkerboards of NRIM satisfying the generalized lens theorem which are host of strongly enhanced electromagnetic feld. Such checkerboards can be mapped using transformational optics onto three-dimensional corner lenses consisting of semi-infinite heterogeneous anisotropic regions of space satisfying the generalized lens theorem. It is also possible to design three-dimensional checkerboards of complementary media, the only restriction being that corresponding unfolded structures in the plane are constrained by the four color theorem. Some of these meta-surfaces in the plane display thin bridges of complementary media, and this further enhances their plasmonic response. Since plasmonic metals mimic the behaviour of NRIM at small length scales, opaque gold films structured at sub-micron scales in a checkerboard fashion were fabricated using focussed-ion-beam technologies and their scattering spectra measured.
A nanodiamond (ND) hosting nitrogen-vacancy (NV) color centers is attached on the apex of an optical tip for near-field microscopy. Its fluorescence is used to launch surface plasmon-polaritons (SPPs) in a thin polycrystalline gold film. It is shown that the quantum nature of the initial source of light is preserved after conversion to SPPs. This opens the way to a deterministic quantum plasmonics, where single SPPs can be injected at well-defined positions in a plasmonic device produced by top-down approaches.
A quantum mechanical approach and local response theory are applied to study plasmons propagating in nanometer-thin gold slabs sandwiched between different dielectrics. The metal slab supports two different kinds of modes, classified as long-range and short-range plasmons. Quantum spill-out is found to significantly increase the imaginary part of their mode indices, and, surprisingly, even for slabs wide enough to approach bulk the increase is 20%. This is explained in terms of enhanced plasmonic absorption, which mainly takes place at narrow peaks located near the slab surface.
Plasmonic waveguides are a promising platform for integrated nanophotonic circuits and nanoscale quantum optics. Their use is however often hampered by the limited propagation length of the guided surface plasmon modes. A detailed understanding of the influence of the material quality and the waveguide geometry on the complex mode index is therefore crucial. In this letter, we present interferometric near-field measurements at telecommunication wavelength on plasmonic slot waveguides fabricated by focused ion beam milling in single- and poly-crystalline gold films. We observe a significantly b…
We have used a gold nanohole array to trap single polystyrene nanoparticles, with a mean diameter of 30 nm, into separated hot spots located at connecting nanoslot regions. A high trap stiffness of approximately 0.85 fN/(nmmW) at a low incident laser intensity of ~0.51 mW/um2 at 980 nm was obtained. The experimental results were compared to the simulated trapping force and a reasonable match was achieved. This plasmonic array is useful for lab-on-a-chip applications and has particular appeal for trapping multiple nanoparticles with predefined separations or arranged in patterns in order to stu…
Electron beam induced deposition (EBID) currently provides the only direct writing technique for truly three-dimensional nanostructures with geometrical features below 50 nm. Unfortunately, the depositions from metal-organic precursors suffer from a substantial carbon content. This hinders many applications, especially in plasmonics where the metallic nature of the geometric surfaces is mandatory. To overcome this problem a post-deposition treatment with oxygen plasma at room temperature was investigated for the purification of gold containing EBID structures. Upon plasma treatment, the struct…
Atomic force microscopy (AFM) nanomanipulation has been viewed as a deterministic method for the assembly of plasmonic metamolecules because it enables unprecedented engineering of clusters with exquisite control over particle number and geometry. Nevertheless, the dimensionality of plasmonic metamolecules via AFM nanomanipulation is limited to 2D, so as to restrict the design space of available artificial electromagnetisms. Here, we show that 2D nanomanipulation of the AFM tip can be used to assemble 3D plasmonic metamolecules in a versatile and deterministic way by dribbling highly spherical…
Plasmonic dark modes are pure near-field resonances since their dipole moments are vanishing in far field. These modes are particularly interesting to enhance nonlinear light-matter interaction at the nanometer scale because radiative losses are mitigated therefore increasing the intrinsic lifetime of the resonances. However, the excitation of dark modes by standard far field approaches is generally inefficient because the symmetry of the electromagnetic near-field distribution has a poor overlap with the excitation field. Here, we demonstrate the selective optical excitation of bright and dar…
Absorbing and emitting optical properties of a spherical plasmonic nanoantenna are described in terms of the size dependent resonance frequencies and damping rates of the multipolar surface plasmons (SP). We provide the plasmon size characteristics for gold and silver spherical particles up to the large size retardation regime where the plasmon radiative damping is significant. We underline the role of the radiation damping in comparison with the energy dissipation damping in formation of receiving and transmitting properties of a plasmonic particle. The size dependence of both: the multipolar…
We experimentally measure and analytically describe the fluorescence enhancement obtained by depositing CdSe/CdS nanocrystals onto a gold plasmonic crystal, a two-dimensional grating of macroscopic size obtained by gold deposition on a self-assembled opal. We show evidences of nanocrystals near-field coupling to the gold Surface Plasmons Polaritons (SPP) followed by grating-induced SPP re-emission to far-field. We develop a theoretical framework and an original method in order to evaluate, from photoluminescence experiments, the SPP extraction efficiency of a grating.
Multiexcitonic transitions and emission of several photons per excitation comprise a very attractive feature of semiconductor quantum dots for optoelectronics applications. However, these higher-order radiative processes are usually quenched in colloidal quantum dots by Auger and other non-radiative decay channels. To increase the multiexcitonic quantum efficiency, several groups have explored plasmonic enhancement, so far with moderate results. By controlled positioning of individual quantum dots in the near field of gold nanocone antennas, we enhance the radiative decay rates of monoexcitons…
In this work, we proposed a high resolution D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor based on gold grating. Gold grating is introduced to modulate the resonance wavelength and enhance the refractive index (RI) sensitivity. Structure parameters of PCF and gold grating are analyzed by finite element method (FEM) for optimizing the SPR sensor. The simulation results indicate that air hole pitch, air hole diameter and gold thickness and grating constant have little influence on the sensitivity of refractive index, which reduces the requirement of precise process…
We discuss the possibility of implementing a novel bio-sensing platform based on the observation of the shift of the leaky surface plasmon mode that occurs at the edge of the plasmonic band gap of metal gratings when an analyte is deposited on top of the metallic structure. We provide experimental proof of the sensing capabilities of a two-dimensional array of gold nano-patches by observing color variations in the diffracted field when the air overlayer is replaced with a small quantity of Isopropyl Alcohol (IPA). Effects of rounded corners and surface imperfections are also discussed. Finally…
Regular arrays of metal nanoparticles on metal films have tuneable optical resonances that can be applied for surface enhanced Raman scattering or biosensing. With the aim of developing more surface selective geometries we investigate regular gold nanoparticle arrays on 25nm thick gold films, which allow to excite asymmetric surface plasmon modes featuring a much better field confinement compared to the symmetric modes used in conventional surface plasmon resonance setups. By optical extinction spectroscopy we identify the plasmonic modes sustained by our structures. Furthermore, the role of t…
The measurement and control of the temperature in microscopic systems, which are increasingly required in diverse applications, are fundamentally important. Yet, the measurement of the three-dimensional (3D) temperature distribution in microscopic systems has not been demonstrated. Here, we propose and experimentally demonstrate the measurement of the 3D temperature distribution by exploiting the temperature dependency of the refractive index (RI). Measurement of the RI distribution of water makes it possible to quantitatively obtain its 3D temperature distribution above a glass substrate coat…
Due to local field enhancement and subwavelength confinements, nano-plasmonics provide numerous novel applications. Simultaneously, as an efficient nanoscale heat generator from inherent absorption, thermo-plasmonics is emerging as an important branch. However, although significant temperature increase is involved in applications, detailed characterization of metal permittivity at different temperatures and corresponding thermo-derivative are lacking. In this work, we extract the permittivity of gold from 300K to the annealing temperature of 570K. By comparing annealed and unannealed films, mo…
Plasmonic platforms are a promising solution for the next generation of low-cost, integrated biomedical sensors. However, fabricating these nanostructures often requires lengthy and challenging fabrication processes. Here we exploit the peculiar features of Focused Ion Beam milling to obtain single-step patterning of a plasmonic two-dimensional (2D) array of truncated gold nano-pyramids (TNP), with gaps as small as 17 nm. We describe the formation of plasmonic bandgaps in the arrangement of crossed tapered grooves that separate the nano-pyramids, and we demonstrate refractive index sensing via…
Longer near-infrared wavelengths provide better penetration depth in biological tissues, so these are useful for plasmonic photothermal cancer therapeutics. In the context of nanoparticles for such applications, the absorption can be tuned for longer NIR wavelengths. However, on increasing the size of the nanoparticle, the scattering is enhanced and thus is not suitable for plasmonic therapeutics. Therefore, to overcome this issue, different types of small gold nanorods were synthesized and converted into stable aggregates to red-shift the plasmonic resonance wavelength to longer near-infrared…
Noble metal nanoparticles show specific optical properties due to the excitation of localized surface plasmons that make them attractive candidates for highly sensitive bionanosensors. The underlying physical principle is either an analyte-induced modification of the dielectric properties of the medium surrounding the nanoparticle or an increase of the excitation and emission rates of an optically active analyte by the resonantly enhanced plasmon field. Either way, besides the nanoparticle geometry the dielectric properties of the metal and nanoscale surface roughness play an important role fo…
Strong Stokes and anti-Stokes one-photon luminescence from single gold nanorods is measured in experiments. It is found that the intensity and polarization of the Stokes and anti-Stokes emissions are in strong correlation. Our experimental observation discovered a coherent process in light emission from single gold nanorods. We present a theoretical mode, based on the concept of cavity resonance, for consistently understanding both Stokes and anti-Stokes photoluminescence. Our theory is in good agreement of all our measurements.
Nanoparticle chain waveguide based on negative-epsilon material is investigated through a generic 3D finite-element Bloch-mode solver which derives complex propagation constant ($k$). Our study starts from waveguides made of non-dispersive material, which not only singles out "waveguide dispersion" but also motivates search of new materials to achieve guidance at unconventional wavelengths. Performances of gold or silver chain waveguides are then evaluated; a concise comparison of these two types of chain waveguides has been previously missing. Beyond these singly-plasmonic chain waveguides, w…
We demonstrate that the fluorescent emitters can increase light emission from the plasmonic nanostructures in turn. With the help of atomic force microscopy, a hybrid system consisting of a fluorescent nanodiamond and a gold nanoparticle was assembled step-by-step for in situ optical measurements. We found that the emission from the nanoparticle increased compared with that before coupling. The interaction between plasmonic nanostructures and fluorescent emitter was understood as an entity based on the concept of a quantized optical cavity by considering the nanodiamond and the nanoparticle as…
A novel method for single-step, lithography-free, and large-scale laser writing of nanoparticle-based plasmonic structures has been developed. Changing energy of femtosecond laser pulses and thickness of irradiated gold film it is possible to vary diameter of the gold nanoparticles, while the distance between them can be varied by laser scanning parameters. This method has an advantage over the most previously demonstrated methods in its simplicity and versatility, while the quality of the structures is good enough for many applications. In particular, resonant light absorbtion/scattering and …
Starting from first principles, we theoretically model the nonlinear temporal dynamics of gold-based plasmonic devices resulting from the heating of their metallic components. At optical frequencies, the gold susceptibility is determined by the interband transitions around the X,L points in the first Brillouin zone and thermo-modulational effects ensue from Fermi smearing of the electronic energy distribution in the conduction band. As a consequence of light-induced heating of the conduction electrons, the optical susceptibility becomes nonlinear. In this paper we describe, for the first time …
We report on fabrication of spatially-coherent columnar plasmonic nanostructure superlattice-type thin films with high porosity and strong optical anisotropy using glancing angle deposition. Subsequent and repeated depositions of silicon and gold lead to nanometer-dimension subcolumns with controlled lengths. The superlattice-type columns resemble bamboo structures where smaller column sections of gold form junctions sandwiched between larger silicon column sections ("nano-bamboo"). We perform generalized spectroscopic ellipsometry measurements and finite element method computations to elucida…
Pulsed laser intensity dependence of crater formation and light reflection in the UDMA-TEGDMA copolymer nanocomposite, doped with resonant plasmonic gold nanorods
Raman spectroscopic characterization of crater walls formed upon single-shot high energy femtosecond laser irradiation of dimethacrylate polymer doped with plasmonic gold nanorods
In this work, we investigate the generation of second harmonic light by gold nanorods and demonstrate that the collected nonlinear intensity depends upon a phase interplay between different modes available in the nanostructure. By recording the backward and forward emitted second harmonic signals from nanorods with various lengths, we find that the maximum nonlinear signal emitted in the forward and backward directions is not obtained for the same nanorod length. We confirm the experimental results with the help of full-wave computations done with a surface integral equation method. These obse…
The development of spintronic technology with increasingly dense, high-speed, and complex devices will be accelerated by accessible microscopy techniques capable of probing magnetic phenomena on picosecond time scales and at deeply sub-micron length scales. A recently developed time-resolved magneto-thermal microscope provides a path towards this goal if it is augmented with a picosecond, nanoscale heat source. We theoretically study adiabatic nanofocusing and near-field heat induction using conical gold plasmonic antennas to generate sub-100 nm thermal gradients for time-resolved magneto-ther…
The scattering and absorption suppression of the silica microspheres is experimentally achieved by semicontinuous gold shell synthesized on the silica microspheres. These fractal gold shells on the silica spheres are shown to have significant extinction in the visible and mid-infrared spectral range. It is found that the silica scattering peak in the visible and the relative contribution of the vibrational stretching band in the infrared gradually decreases with increasing of the gold coverage.
Excitation of coherent optical phonons in solids provides a pathway for ultrafast modulation of light on a sub-ps timescale. Here, we report on efficient 3.6 THz modulation of light reflected from hybrid metal/semiconductor plasmonic crystals caused by lattice vibrations in a few nm thick layer of elemental tellurium. We observe that surface plasmon polaritons contribute significantly to photoinduced formation of this thin layer at the interface between a telluride-based II-VI semiconductor, such as (Cd,Mg)Te or (Cd,Mn)Te, and a one-dimensional gold grating. The change in interface composition…
Motivated by the recent renewed interest in compact analog computing using light and metasurfaces (Silva, A. et al., Science 2014, 343, 160-163), we suggest a practical approach to its realization that involves reflective metasurfaces consisting of arrayed gold nanobricks atop a subwavelength-thin dielectric spacer and optically-thick gold film, a configuration that supports gap-surface plasmon resonances. Using well established numerical routines, we demonstrate that these metasurfaces enable independent control of the light phase and amplitude, and design differentiator and integrator metasu…
Here we demonstrate the gas sensing ability of cavity-coupled metallic nanoparticle systems, comprising gold nanoparticles separated from a gold mirror with a polymer spacer. An increase in relative humidity (RH) causes the spacer to expand, which induces a significant reduction of nanoparticle scattering intensity, as the scattering is highly dependent on the cavity-nanoparticle coupling that closely relates to the nanoparticle-mirror distance. This lithography-free structure enables a remarkable averaging sensitivity at 0.12 dB/% RH and 0.25 dB/% RH over RH range (45-75%), possessing an esti…
Exceptional broadband absorption of nanoporous gold explained by plasmonic resonances at dangling ligaments
Hamburg University of Technology（汉堡工业大学）；Institute of Optical and Electronic Materials, Hamburg University of Technology（汉堡工业大学光学与电子材料研究所）；Helmholtz-Zentrum Geesthacht（赫尔姆霍茨盖斯特哈赫特中心）；Institute of Functional Materials for Sustainability, Helmholtz-Zentrum Geesthacht（赫尔姆霍茨盖斯特哈赫特中心可持续功能材料研究所）
We report a novel approach for on-chip electrical detection of the radiation guided by dielectric-loaded surface plasmon polariton waveguides (DLSPPW) and DLSPPW-based components. The detection is realized by fabricating DLSPPW components on the surface of a gold (Au) pad supported by a silicon (Si) substrate supplied with aluminum pads facilitating electrical connections, with the gold pad being perforated in a specific locations below the DLSPPWs in order to allow a portion of the DLSPPW-guided radiation to leak into the Si-substrate, where it is absorbed and electrically detected. We presen…
Deep subwavelength integration of high-definition plasmonic nanostructures is of key importance for the development of future optical nanocircuitry for high-speed communication, quantum computation and lab-on-a-chip applications. So far the experimental realization of proposed extended plasmonic networks consisting of multiple functional elements remains challenging, mainly due to the multi-crystallinity of commonly used thermally evaporated gold layers. Resulting structural imperfections in individual circuit elements will drastically reduce the yield of functional integrated nanocircuits. He…
The absorptance of p-polarized light in superconducting-nanowire single-photon detectors (SNSPDs) was improved by integrating (1) ~quarter-wavelength nano-optical cavity closed by a gold reflector (OC-SNSPD), (2) nano-cavity-array closed by vertical and horizontal gold segments (NCAI-SNSPD), and (3) nano-cavity-deflector-array consisting of longer vertical gold segments (NCDAI-SNSPD) into short- (p-) and long- (3p-) periodic niobium-nitride (NbN) stripe-patterns. In OC-SNSPDs the highest absorptance is observable at perpendicular incidence onto NbN stripes in P-orientation due to E-field conce…
We report the results of theoretical and experimental studies of photoluminescence of silicon nanocrystals in the proximity of plasmonic modes of different types. In our samples, the type of plasmonic mode is determined by the filling ratio of a one-dimensional gold grating which covers the thin film with silicon nanocrystals on a quartz substrate. We analyze the extinction and photoluminesce spectra of silicon nanocrystals and show that the emitted light is coupled to the corresponding plasmonic mode. We also demonstrate the modification of the extinction and photoluminesce spectra under the …
In this work, we present a novel technique to directly measure the phase shift of the optical signal scattered by single plasmonic nanoparticles in a diffraction-limited laser focus. We accomplish this by equipping an inverted confocal microscope with a Michelson interferometer and scanning single nanoparticles through the focal volume while recording interferograms of the scattered and a reference wave for each pixel. For the experiments, lithographically prepared gold nanorods where used, since their plasmon resonances can be controlled via their aspect ratio. We have developed a theoretical…
We demonstrate `deterministic' launching of propagative quantum surface-plasmon polaritons at freely chosen positions on gold plasmonic receptacles. This is achieved by using as plasmon launcher a near-field scanning optical source made of a diamond nanocrystal with two Nitrogen-Vacancy color-center occupancy. Our demonstration relies on leakage-radiation microscopy of a thin homogeneous gold film and on near-field optical microscopy of a nanostructured thick gold film. Our work paves the way to future fundamental studies and applications in quantum plasmonics that require an accurate position…
The influence of the orientation of gold nanorods in different assemblies has been investigated using the Finite Difference Time Domain (FDTD) simulation method. To understand the relative orientation, we vary the size and angle in dimer geometries. Significant effects of plasmon coupling emerged in longitudinal resonances having end-to-end configurations of gold nanorods. The effect of orientational plasmon coupling in dimers gives rise to both bonding and anti-bonding plasmon modes. Effects of various geometries like primary monomer, dimer, trimer, and tetramer structures have been explored …
Surface Plasmon Resonance sensors are a well-established class of sensors which includes a very large variety of materials and detection schemes. However, the development of portable devices is still challenging as due to the intrinsic complexity of the optical excitation/detection schemes. In this work we show that Nanoporous gold (NPG) films may overcome these limitations by providing excellent sensitivity without the need of sophisticated fabrication approaches and/or optical setup. The sensing mechanism is related the co-localization of optical energy and analytes into the pores that promo…
We investigate the plasmonic nanohelix as an individual subwavelength element for locally probing light chirality. We show that an hybrid nanoantenna combining a carbon-gold core-shell helix and a plasmonic nanoaperture transmits circularly polarized light with the same handedness as the helix and blocks the other. Such an assymmetric response is spatially localized, spectrally broadband and background-free. Finally, we demonstrate the possibility to engineer an individual plasmonic helix at the apex of a sharp tip typically used in scanning near-field microscopies, thus opening the prospect o…
Confining light in extreme subwavelength scales is a tantalizing task. In this work, we report a study of individual plasmonic film-coupled nanostar resonators where plasmonic optical modes are trapped in ultrasmall volumes. Individual gold nanostars, separated from a flat gold film by a thin dielectric spacer layer, exhibit a strong light confinement within the sub-10 nm volume of the nanostar's tips and the film. Through dark field scattering measurements of many individual nanostars, a statistical observation of the scattered spectra is obtained and compared with extensive simulation data t…
Recently, nonlinear hybrid metasurface comes into an attractive new concept in the research of nanophotonics and nanotechnology. It is composed of semiconductors with an intrinsically large nonlinear susceptibility and traditional plasmonic metasurfaces, offering opportunities for efficiently generating and manipulating nonlinear optical responses. A high second-harmonic generation (SHG) conversion efficiency has been demonstrated in the mid-infrared region by using multi-quantum-well (MQW) based plasmonic metasurfaces. However, it has yet to be demonstrated in the visible region. Here we pres…
We show that the positioning of a nanometer length scale dielectric object, such as a diamond nanocrystal, in the vicinity of a gold bowtie nanoantenna can be used to tune the plasmonic mode spectrum on the order of a linewidth. We further show that the intrinsic luminescence of gold enhanced in the presence of nanometer-scale roughness couples efficiently to the plasmon mode and carries the same polarization anisotropy. Our findings have direct implications for cavity quantum electrodynamics related applications of hybrid antenna-emitter complexes.
Spatially Uniform and Defect-Tolerant Plasmonic Responses in 3D printed Gold Nanoparticle Assemblies
Paderborn University（帕德博恩大学）；Kumoh National Institute of Technology（龟尾国立科学技术院）；Gumi Electronics & Information Technology Research Institute（龟尾电子信息技术研究院）；Hallym University（韩国基督教大学）
The propagation of plasmonic waves in various metallic quantum nanostructures have considered attention for their applications in technology. The quantum plasmonic properties of metallic nanostructures in the quantum size regime have been difficult to describe by an appropriate model. Here the nonlocal quantum plasmons are investigated in the most important metals of copper, gold, and silver. Dispersion properties of these metals and propagation of longitudinal quantum plasmons in the high photon energy regime are studied by a new model of nonlocal quantum dielectric permittivity. The epsilon …
Photothermal surface bubbles play important roles in a wide range of applications like catalysis, microfluidics and biosensing, but their formation on a transparent substrate immersed in a plasmonic nanoparticle (NP) suspension has an unknown origin. Here, we show that NPs deposited on the substrate by dispersive optical forces are responsible for the nucleation of such photothermal surface bubbles. High-speed videography shows that the surface bubble formation is always preceded by the optically driven NPs moving toward and adhering to the surface. We observe that the thresholds of laser powe…
