41 results found
Albella Echave P, Shibanuma T, Maier S, 2016, Unidirectional light scattering with high efficiency at optical frequencies based on low-loss dielectric nanoantennas, Nanoscale, Vol: 8, Pages: 14184-14192, ISSN: 2040-3372
Dielectric nanoparticles offer low optical losses and access to both electric and magnetic Mie resonances. This enables unidirectional scattering along the incident axis of light, owing to the interference between these two resonances. Here we theoretically and experimentally demonstrate that an asymmetric dimer of dielectric nanoparticles can provide unidirectional forward scattering with high efficiency. Theoretical analyses reveal that the dimer configuration can satisfy the first Kerker condition at the resonant peaks of electric and magnetic dipolar modes, therefore showing highly efficient directional forward scattering. The unidirectional forward scattering with high efficiency is confirmed in our experiments using a silicon nanodisk dimer on a transparent substrate. This study will boost the realization of practical applications using low-loss and efficient subwavelength all-dielectric nanoantennas.
Maier SA, Ma Z, Hanham, et al., 2016, Terahertz All-Dielectric Magnetic MirrorMetasurfaces, ACS Photonics, Vol: 3, Pages: 1010-1018, ISSN: 2330-4022
We demonstrate an all-dielectric metasurface operating in the terahertz band that is capable of engineering a reflected beam’s spatial properties with high efficiency. The metasurface is formed from an array of silicon cube resonators which simultaneously support electric and magnetic dipolar Mie resonances. By controlling the interference between these modes, the amplitude and phase of a reflected wave can be arbitrarily controlled over a subwavelength area. We demonstrate the flexibility and utility of this metasurface by optimizing the surface to produce several reflected beam types including vortex and Bessel beams; the latter being useful for diffraction-free point-to-point terahertz communications. Additionally, we show theoretically and experimentally how the metasurface can produce an all-dielectric magnetic mirror in the terahertz band.
Freedman KJ, Crick CR, Albella P, et al., 2016, On-Demand Surface and Tip Enhanced Raman Spectroscopy Using Dielectrophoretic Trapping and Nanopore Sensing, ACS Photonics, Vol: 3, Pages: 1036-1044, ISSN: 2330-4022
Surface enhanced Raman spectroscopy (SERS) and tip-enhanced Raman Spectroscopy (TERS) have shown great promise in the detection and analysis of trace analytes throughout numerous fields of study. Both SERS and TERS utilize nanoscale plasmonic surface features to increase the intensity of observed Raman signals by many orders of magnitude (> 108). One of the major factors limiting the wider and more routine implementation of the enhanced Raman phenomena, is in the difficulty of forming consistent and reliable plasmonic substrates with well defined “hot-spots”. We address this limitation by designing a platform which can be used for both SERS and TERS respectively. The presented technique allows for rapid, controlled, “on-demand”, and reversible formation of a SERS substrate using dielectrophorisis (DEP) at the end of a nanoscale pipette. This drives gold nanoparticles in solution to concentrate and self-assemble at the tip of the pipette, where analytes can be detected effectively using SERS. An additional benefit of the platform is that the nanopipette containing a nanopore can be used for detection of individual nanoparticles facilitated by the added enhancement originating from the nanopipette tip enhanced signal. Complementing the experimental results are simulations highlighting the mechanism for SERS substrate formation and TERS detection.
Della Picca F, Berte R, Rahmani M, et al., 2016, Tailored Hypersound Generation in Single Plasmonic Nanoantennas., Nano Letters, Vol: 16, Pages: 1428-1434, ISSN: 1530-6992
Ultrashort laser pulses impinging on a plasmonic nanostructure trigger a highly dynamic scenario in the interplay of electronic relaxation with lattice vibrations, which can be experimentally probed via the generation of coherent phonons. In this Letter, we present studies of hypersound generation in the range of a few to tens of gigahertz on single gold plasmonic nanoantennas, which have additionally been subjected to predesigned mechanical constraints via silica bridges. Using these hybrid gold/silica nanoantennas, we demonstrate experimentally and via numerical simulations how mechanical constraints allow control over their vibrational mode spectrum. Degenerate pump-probe techniques with double modulation are performed in order to detect the small changes produced in the probe transmission by the mechanical oscillations of these single nanoantennas.
Albella P, Shibanuma T, Maier S, 2015, Switchable directional scattering of electromagnetic radiation with subwavelength asymmetric silicon dimers, Scientific Reports, Vol: 5, ISSN: 2045-2322
High refractive index dielectric nanoparticles show high promise as a complementary nanophotonics platform due to compared with plasmonic nanostructures low absorption losses and the co-existence of magnetic and electric resonances. Here we explore their use as resonantly enhanced directional scatterers.We theoretically demonstrate that an asymmetric dimer of silicon nanoparticles shows tuneable directional scattering depending on the frequency of excitation. This is due to the interference between dipoles excited in each nanoparticle, enabling directional control of the scattered light. Interestingly, this control can be achieved regardless of the polarization direction with respect to the dimer axis; however, difference in the polarization can shift the wavelengths at which the directional scattering is achieved. We also explore the application of such an asymmetric nanoantenna as a tuneable routing element in a nanometer scale a full numerical simulation, suggesting applications in optical nanocircuitry.
Caldarola M, Albella P, Cortés E, et al., 2015, Non-plasmonic nanoantennas for surface enhanced spectroscopies with ultra-low heat conversion, Nature Communications, Vol: 6, ISSN: 2041-1723
Nanoplasmonics has recently revolutionized our ability to control light on the nanoscale. Using metallic nanostructures with tailored shapes, it is possible to efficiently focus light into nanoscale field 'hot spots'. High field enhancement factors have been achieved in such optical nanoantennas, enabling transformative science in the areas of single molecule interactions, highly enhanced nonlinearities and nanoscale waveguiding. Unfortunately, these large enhancements come at the price of high optical losses due to absorption in the metal, severely limiting real-world applications. Via the realization of a novel nanophotonic platform based on dielectric nanostructures to form efficient nanoantennas with ultra-low light-into-heat conversion, here we demonstrate an approach that overcomes these limitations. We show that dimer-like silicon-based single nanoantennas produce both high surface enhanced fluorescence and surface enhanced Raman scattering, while at the same time generating a negligible temperature increase in their hot spots and surrounding environments.
Rakovich A, Albella P, Maier SA, 2015, Plasmonic Control of Radiative Properties of Semiconductor Quantum Dots Coupled to Plasmonic Ring Cavities, ACS NANO, Vol: 9, Pages: 2648-2658, ISSN: 1936-0851
Crick CR, Albella P, Ng B, et al., 2014, Precise Attolitre Temperature Control of Nanopore Sensors using a Nanoplasmonic Bullseye, Nano Letters, Vol: 15, Pages: 553-559, ISSN: 1530-6992
Targeted temperature control in nanopores isgreatly important in further understanding biological molecules.Such control would extend the range of examinablemolecules and facilitate advanced analysis, including thecharacterization of temperature-dependent molecule conformations.The work presented within details well-definedplasmonic gold bullseye and silicon nitride nanoporemembranes. The bullseye nanoantennae are designed andoptimized using simulations and theoretical calculations forinteraction with 632.8 nm laser light. Laser heating wasmonitored experimentally through nanopore conductancemeasurements. The precise heating of nanopores is demonstratedwhile minimizing the accumulation of heat in the surrounding membrane material
Osorio-Roman IO, Guerrero AR, Albella P, et al., 2014, Plasmon Enhanced Fluorescence with Aggregated Shell-Isolated Nanoparticles, ANALYTICAL CHEMISTRY, Vol: 86, Pages: 10246-10251, ISSN: 0003-2700
Albella P, Alcaraz de la Osa R, Moreno F, et al., 2014, Electric and Magnetic Field Enhancement with Ultralow Heat Radiation Dielectric Nanoantennas: Considerations for Surface-Enhanced Spectroscopies, ACS PHOTONICS, Vol: 1, Pages: 524-529, ISSN: 2330-4022
Albella P, Ameen Poyli M, Schmidt MK, et al., 2013, Low-Loss Electric and Magnetic Field-Enhanced Spectroscopy with Subwavelength Silicon Dimers, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 117, Pages: 13573-13584, ISSN: 1932-7447
Moreno F, Albella P, Nieto-Vesperinas M, 2013, Analysis of the Spectral Behavior of Localized Plasmon Resonances in the Near- and Far-Field Regimes, LANGMUIR, Vol: 29, Pages: 6715-6721, ISSN: 0743-7463
Alonso-Gonzalez P, Albella P, Neubrech F, et al., 2013, Experimental Verification of the Spectral Shift between Near- and Far-Field Peak Intensities of Plasmonic Infrared Nanoantennas, PHYSICAL REVIEW LETTERS, Vol: 110, ISSN: 0031-9007
Alonso-Gonzalez P, Albella P, Golmar F, et al., 2013, Visualizing the near-field coupling and interference of bonding and anti-bonding modes in infrared dimer nanoantennas, OPTICS EXPRESS, Vol: 21, Pages: 1270-1280, ISSN: 1094-4087
Moula G, Rodriguez-Oliveros R, Albella P, et al., 2012, Plasmonics and single-molecule detection in evaporated silver-island films, Annalen der Physik, Vol: 524, Pages: 697-704, ISSN: 0003-3804
Abb M, Wang Y, Albella P, et al., 2012, Interference, coupling, and nonlinear control of high-order modes in single asymmetric nanoantennas., ACS nano, Vol: 6, Pages: 6462-70, ISSN: 1936-086X
We investigate theoretically and experimentally the structure of plasmonic modes in individual asymmetric dimer antennas. Plasmonic near-field coupling of high-order modes results in hybridization of bright and dark modes of the individual nanorods, leading to an anticrossing of the coupled resonances. For two bright modes, hybridization results in a capacitive red shift and super-radiant broadening. We show that the properties of asymmetric dimers can be used for nonlinear control of spectral modes and demonstrate such a nonlinear effect by measuring the modulation of a hybrid asymmetric dimer–ITO antenna. With use of full electrodynamical calculations, we find that the properties of the near-field nonlinear responses are distinctly different from the far-field, which opens up new routes for nonlinear control of plasmonic nanosystems.
Berrier A, Albella P, Poyli MA, et al., 2012, Detection of deep-subwavelength dielectric layers at terahertz frequencies using semiconductor plasmonic resonators., Optics express, Vol: 20, Pages: 5052-60, ISSN: 1094-4087
Plasmonic bowtie antennas made of doped silicon can operate as plasmonic resonators at terahertz (THz) frequencies and provide large field enhancement close to their gap. We demonstrate both experimentally and theoretically that the field confinement close to the surface of the antenna enables the detection of ultrathin (100 nm) inorganic films, about 3750 times thinner than the free space wavelength. Based on model calculations, we conclude that the detection sensitivity and its variation with the thickness of the deposited layer are related to both the decay of the local THz field profile around the antenna and the local field enhancement in the gap of the bowtie antenna. This large field enhancement has the potential to improve the detection limits of plasmon-based biological and chemical sensors.
Geffrin JM, García-Cámara B, Gómez-Medina R, et al., 2012, Magnetic and electric coherence in forward- and back-scattered electromagnetic waves by a single dielectric subwavelength sphere., Nature communications, Vol: 3, Pages: 1171-1171, ISSN: 2041-1723
Magnetodielectric small spheres present unusual electromagnetic scattering features, theoretically predicted a few decades ago. However, achieving such behaviour has remained elusive, due to the non-magnetic character of natural optical materials or the difficulty in obtaining low-loss highly permeable magnetic materials in the gigahertz regime. Here we present unambiguous experimental evidence that a single low-loss dielectric subwavelength sphere of moderate refractive index (n=4 like some semiconductors at near-infrared) radiates fields identical to those from equal amplitude crossed electric and magnetic dipoles, and indistinguishable from those of ideal magnetodielectric spheres. The measured scattering radiation patterns and degree of linear polarization (3-9 GHz/33-100 mm range) show that, by appropriately tuning the a/λ ratio, zero-backward (’Huygens’ source) or almost zero-forward (’Huygens’ reflector) radiated power can be obtained. These Kerker scattering conditions only depend on a/λ. Our results open new technological challenges from nano- and micro-photonics to science and engineering of antennas, metamaterials and electromagnetic devices.
Alonso-González P, Albella P, Schnell M, et al., 2012, Resolving the electromagnetic mechanism of surface-enhanced light scattering at single hot spots., Nature communications, Vol: 3, Pages: 684-684, ISSN: 2041-1723
Light scattering at nanoparticles and molecules can be dramatically enhanced in the ’hot spots’ of optical antennas, where the incident light is highly concentrated. Although this effect is widely applied in surface-enhanced optical sensing, spectroscopy and microscopy, the underlying electromagnetic mechanism of the signal enhancement is challenging to trace experimentally. Here we study elastically scattered light from an individual object located in the well-defined hot spot of single antennas, as a new approach to resolve the role of the antenna in the scattering process. We provide experimental evidence that the intensity elastically scattered off the object scales with the fourth power of the local field enhancement provided by the antenna, and that the underlying electromagnetic mechanism is identical to the one commonly accepted in surface-enhanced Raman scattering. We also measure the phase shift of the scattered light, which provides a novel and unambiguous fingerprint of surface-enhanced light scattering.
Aroca RF, Teo GY, Mohan H, et al., 2011, Plasmon-Enhanced Fluorescence and Spectral Modification in SHINEF, The Journal of Physical Chemistry C, Vol: 115, Pages: 20419-20424, ISSN: 1932-7447
Albella P, Garcia-Cueto B, Gonzalez F, et al., 2011, Shape Matters: Plasmonic Nanoparticle Shape Enhances Interaction with Dielectric Substrate, NANO LETTERS, Vol: 11, Pages: 3531-3537, ISSN: 1530-6984
Albella P, María Saiz J, González F, et al., 2011, Surface monitoring based on light scattering by metal nanosensors, Journal of Quantitative Spectroscopy and Radiative Transfer, Vol: 112, Pages: 2046-2058, ISSN: 0022-4073
Alonso-Gonzalez P, Schnell M, Sarriugarte P, et al., 2011, Real-space mapping of Fano interference in plasmonic metamolecules., Nano letters, Vol: 11, Pages: 3922-6, ISSN: 1530-6992
An unprecedented control of the spectral response of plasmonic nanoantennas has recently been achieved by designing structures that exhibit Fano resonances. This new insight is paving the way for a variety of applications, such as biochemical sensing and surface-enhanced Raman spectroscopy. Here we use scattering-type near-field optical microscopy to map the spatial field distribution of Fano modes in infrared plasmonic systems. We observe in real space the interference of narrow (dark) and broad (bright) plasmonic resonances, yielding intensity and phase toggling between different portions of the plasmonic metamolecules when either their geometric sizes or the illumination wavelength is varied.
Weber D, Albella P, Alonso-González P, et al., 2011, Longitudinal and transverse coupling in infrared gold nanoantenna arrays: long range versus short range interaction regimes., Optics express, Vol: 19, Pages: 15047-61, ISSN: 1094-4087
Interaction between micrometer-long nanoantennas within an array considerably modifies the plasmonic resonant behaviour; for fundamental resonances in the infrared already at micrometer distances. In order to get systematic knowledge on the relationship between infrared plasmonic resonances and separation distances dx and dy in longitudinal and transverse direction, respectively, we experimentally studied the optical extinction spectra for rectangularly ordered lithographic gold nanorod arrays on silicon wafers. For small dy, strong broadening of resonances and strongly decreased values of far-field extinction are detected which come along with a decreased near-field intensity, as indicated by near-field amplitude maps of the interacting nanoantennas. In contrast, near-field interaction over small dx does only marginally broaden the resonance. Our findings set a path for optimum design of rectangular nanorod lattices for surface enhanced infrared spectroscopy.
Abb M, Albella P, Aizpurua J, et al., 2011, All-optical control of a single plasmonic nanoantenna-ITO hybrid., Nano letters, Vol: 11, Pages: 2457-63, ISSN: 1530-6992
We demonstrate experimentally picosecond all-optical control of a single plasmonic nanoantenna embedded in indium tin oxide (ITO). We identify a picosecond response of the antenna-ITO hybrid system, which is distinctly different from transient bleaching observed for gold antennas on a nonconducting SiO(2) substrate. Our experimental results can be explained by the large free-carrier nonlinearity of ITO, which is enhanced by plasmon-induced hot-electron injection from the gold nanoantenna into the conductive oxide. The combination of tunable antenna-ITO hybrids with nanoscale plasmonic energy transfer mechanisms, as demonstrated here, opens a path for new ultrafast devices to produce nanoplasmonic switching and control.
Albella P, Gonzalez F, Moreno F, et al., 2011, Detection and Characterization of Nano-Defects Located on Micro-Structured Substrates by Means of Light Scattering, Wave Propagation, Editors: Petrin, Publisher: Intech
Paniagua-Domínguez R, Sánchez-Gil JA, Albella P, et al., 2010, Enhanced backscattering of electromagnetic waves from randomly rough gratings on negative magnetic metamaterials, Metamaterials, Vol: 4, Pages: 201-206, ISSN: 1873-1988
Alcaraz de la Osa R, Albella P, Saiz JM, et al., 2010, Extended discrete dipole approximation and its application to bianisotropic media, OPTICS EXPRESS, Vol: 18, Pages: 23865-23871, ISSN: 1094-4087
Setién B, Albella P, Saiz JM, et al., 2010, Spectral behavior of the linear polarization degree at right-angle scattering configuration for nanoparticle systems, New Journal of Physics, Vol: 12, Pages: 103031-103031, ISSN: 1367-2630
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