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ACS Photonics

Magdalena Schatzl, Florian Hackl, Martin Glaser, Patrick Rauter, Moritz Brehm, Lukas Spindlberger, Angelica Simbula, Matteo Galli, Thomas Fromherz, Friedrich Schäffler
Efficient coupling to integrated high-quality-factor cavities is crucial for the employment of germanium quantum dot (QD) emitters in future monolithic silicon-based optoelectronic platforms. We report on strongly enhanced emission from single Ge QDs into L3 photonic crystal resonator (PCR) modes based on precise positioning of these dots at the maximum of the respective mode field energy density. Perfect site control of Ge QDs grown on prepatterned silicon-on-insulator substrates was exploited to fabricate in one processing run almost 300 PCRs containing single QDs in systematically varying positions within the cavities...
March 15, 2017: ACS Photonics
Daniel Cole, Gavin Young, Alexander Weigel, Aleksandar Sebesta, Philipp Kukura
Our ability to optically interrogate nanoscopic objects is controlled by the difference between their extinction cross sections and the diffraction-limited area to which light can be confined in the far field. We show that a partially transmissive spatial mask placed near the back focal plane of a high numerical aperture microscope objective enhances the extinction contrast of a scatterer near an interface by approximately T(-1/2), where T is the transmissivity of the mask. Numerical-aperture-based differentiation of background from scattered light represents a general approach to increasing extinction contrast and enables routine label-free imaging down to the single-molecule level...
February 15, 2017: ACS Photonics
Christian Kramer, Martin Schäferling, Thomas Weiss, Harald Giessen, Tobias Brixner
We present an analytic derivation for the enhancement of local optical chirality in the near field of plasmonic nanostructures by tuning the far-field polarization of external light. We illustrate the results by means of simulations with an achiral and a chiral nanostructure assembly and demonstrate that local optical chirality is significantly enhanced with respect to circular polarization in free space. The optimal external far-field polarizations are different from both circular and linear. Symmetry properties of the nanostructure can be exploited to determine whether the optimal far-field polarization is circular...
February 15, 2017: ACS Photonics
Diego M Solís, José M Taboada, Fernando Obelleiro, Luis M Liz-Marzán, F Javier García de Abajo
Surface-enhanced Raman scattering (SERS) has become a widely used spectroscopic technique for chemical identification, providing unbeaten sensitivity down to the single-molecule level. The amplification of the optical near field produced by collective electron excitations -plasmons- in nanostructured metal surfaces gives rise to a dramatic increase by many orders of magnitude in the Raman scattering intensities from neighboring molecules. This effect strongly depends on the detailed geometry and composition of the plasmon-supporting metallic structures...
February 15, 2017: ACS Photonics
Alessandro Alberucci, Chandroth P Jisha, Lorenzo Marrucci, Gaetano Assanto
We investigate electromagnetic propagation in uniaxial dielectrics with a transversely varying orientation of the optic axis, the latter staying orthogonal everywhere in the propagation direction. In such a geometry, the field experiences no refractive index gradients, yet it acquires a transversely modulated Pancharatnam-Berry phase, that is, a geometric phase originating from a spin-orbit interaction. We show that the periodic evolution of the geometric phase versus propagation gives rise to a longitudinally invariant effective potential...
December 21, 2016: ACS Photonics
Yuriy Zakharko, Martin Held, Arko Graf, Tobias Rödlmeier, Ralph Eckstein, Gerardo Hernandez-Sosa, Bernd Hähnlein, Jörg Pezoldt, Jana Zaumseil
Hybrid photonic-plasmonic modes in periodic arrays of metallic nanostructures offer a promising trade-off between high-quality cavities and subdiffraction mode confinement. However, their application in electrically driven light-emitting devices is hindered by their sensitivity to the surrounding environment and to charge injecting metallic electrodes in particular. Here, we demonstrate that the planar structure of light-emitting field-effect transistor (LEFET) ensures undisturbed operation of the characteristic modes...
December 21, 2016: ACS Photonics
J Cuerda, F J García-Vidal, J Bravo-Abad
Nanoscale laser sources based on single metallic nanoparticles (spasers) have attracted significant interest for their fundamental implications and technological potential. Here we theoretically investigate the spatio-temporal dynamics of lasing action in core-shell metallic nanoparticles that include optically pumped four-level gain media. By using detailed semiclassical simulations based on a time-domain generalization of the finite-element method, we study the evolution of the lasing dynamics when going from a spherical case to an elongated nanorod configuration...
October 19, 2016: ACS Photonics
James A Dolan, Matthias Saba, Raphael Dehmel, Ilja Gunkel, Yibei Gu, Ulrich Wiesner, Ortwin Hess, Timothy D Wilkinson, Jeremy J Baumberg, Ullrich Steiner, Bodo D Wilts
Gold gyroid optical metamaterials are known to possess a reduced plasma frequency and linear dichroism imparted by their intricate subwavelength single gyroid morphology. The anisotropic optical properties are, however, only evident when a large individual gyroid domain is investigated. Multidomain gyroid metamaterials, fabricated using a polyisoprene-b-polystyrene-b-poly(ethylene oxide) triblock terpolymer and consisting of multiple small gyroid domains with random orientation and handedness, instead exhibit isotropic optical properties...
October 19, 2016: ACS Photonics
Rolf Szedlak, Andreas Harrer, Martin Holzbauer, Benedikt Schwarz, Johannes Paul Waclawek, Donald MacFarland, Tobias Zederbauer, Hermann Detz, Aaron Maxwell Andrews, Werner Schrenk, Bernhard Lendl, Gottfried Strasser
The ubiquitous trend toward miniaturized sensing systems demands novel concepts for compact and versatile spectroscopic tools. Conventional optical sensing setups include a light source, an analyte interaction region, and a separate external detector. We present a compact sensor providing room-temperature operation of monolithic surface-active lasers and detectors integrated on the same chip. The differentiation between emitter and detector is eliminated, which enables mutual commutation. Proof-of-principle gas measurements with a limit of detection below 400 ppm are demonstrated...
October 19, 2016: ACS Photonics
Anouk de Hoogh, Aron Opheij, Matthias Wulf, Nir Rotenberg, L Kuipers
We present experimental observations of visible wavelength second- and third-harmonic generation on single plasmonic nanowires of variable widths. We identify that near-infrared surface plasmon polaritons, which are guided along the nanowire, act as the source of the harmonics generation. We discuss the underlying mechanism of this nonlinear process, using a combination of spatially resolved measurements and numerical simulations to show that the visible harmonics are generated via a combination of both local and propagating plasmonic modes...
August 17, 2016: ACS Photonics
Joshua S Ostrander, Arnaldo L Serrano, Ayanjeet Ghosh, Martin T Zanni
We report the first wide-field microscope for measuring two-dimensional infrared (2D IR) spectroscopic images. We concurrently collect more than 16 000 2D IR spectra, made possible by a new focal plane array detector and mid-IR pulse shaping, to generate hyperspectral images with multiple frequency dimensions and diffraction-limited spatial resolution. Both frequency axes of the spectra are collected in the time domain by scanning two pairs of femtosecond pulses using a dual acousto-optic modulator pulse shaper...
July 20, 2016: ACS Photonics
Johannes Ziegler, Christian Wörister, Cynthia Vidal, Calin Hrelescu, Thomas A Klar
Huge spectral coverage of random lasing throughout the visible up to the infrared range is achieved with star-shaped gold nanoparticles ("nanostars"). As intrinsically broadband scattering centers, the nanostars are suspended in solutions of various laser dyes, forming randomly arranged resonators which support coherent laser modes. The narrow emission line widths of 0.13 nm or below suggest that gold nanostars provide an efficient coherent feedback for random lasers over an extensive range of wavelengths, all together spanning almost a full optical octave from yellow to infrared...
June 15, 2016: ACS Photonics
Nan Guan, Xing Dai, Agnès Messanvi, Hezhi Zhang, Jianchang Yan, Eric Gautier, Catherine Bougerol, François H Julien, Christophe Durand, Joël Eymery, Maria Tchernycheva
We report the first demonstration of flexible white phosphor-converted light emitting diodes (LEDs) based on p-n junction core/shell nitride nanowires. GaN nanowires containing seven radial In0.2Ga0.8N/GaN quantum wells were grown by metal-organic chemical vapor deposition on a sapphire substrate by a catalyst-free approach. To fabricate the flexible LED, the nanowires are embedded into a phosphor-doped polymer matrix, peeled off from the growth substrate, and contacted using a flexible and transparent silver nanowire mesh...
April 20, 2016: ACS Photonics
Anna Lombardi, Angela Demetriadou, Lee Weller, Patrick Andrae, Felix Benz, Rohit Chikkaraddy, Javier Aizpurua, Jeremy J Baumberg
The near-field and far-field spectral response of plasmonic systems are often assumed to be identical, due to the lack of methods that can directly compare and correlate both responses under similar environmental conditions. We develop a widely tunable optical technique to probe the near-field resonances within individual plasmonic nanostructures that can be directly compared to the corresponding far-field response. In tightly coupled nanoparticle-on-mirror constructs with nanometer-sized gaps we find >40 meV blue-shifts of the near-field compared to the dark-field scattering peak, which agrees with full electromagnetic simulations...
March 16, 2016: ACS Photonics
Martyna Grydlik, Florian Hackl, Heiko Groiss, Martin Glaser, Alma Halilovic, Thomas Fromherz, Wolfgang Jantsch, Friedrich Schäffler, Moritz Brehm
Semiconductor light-emitters compatible with standard Si integration technology (SIT) are of particular interest for overcoming limitations in the operating speed of microelectronic devices. Light sources based on group IV elements would be SIT-compatible, but suffer from the poor optoelectronic properties of bulk Si and Ge. Here we demonstrate that epitaxially grown Ge quantum dots (QDs) in a defect-free Si matrix show extraordinary optical properties if partially amorphized by Ge-ion bombardment (GIB). In contrast to conventional SiGe nanostructures, these QDs exhibit dramatically shortened carrier lifetimes and negligible thermal quenching of the photoluminescence (PL) up to room temperature...
February 17, 2016: ACS Photonics
Yuriy Zakharko, Martin Held, Fabrizio-Zagros Sadafi, Florentina Gannott, Ali Mahdavi, Ulf Peschel, Robin N Klupp Taylor, Jana Zaumseil
The ability to confine and manipulate light below the diffraction limit is a major goal of future multifunctional optoelectronic/plasmonic systems. Here, we demonstrate the design and realization of a tunable and localized electrical source of excitons coupled to surface plasmons based on a polymer light-emitting field-effect transistor (LEFET). Gold nanorods that are integrated into the channel support localized surface plasmons and serve as nanoantennas for enhanced electroluminescence. By precise spatial control of the near-infrared emission zone in the LEFET via the applied voltages the near-field coupling between electrically generated excitons and the nanorods can be turned on or off as visualized by a change of electroluminescence intensity...
January 20, 2016: ACS Photonics
Jungseok Chae, Basudev Lahiri, Andrea Centrone
Engineering of the optical resonances in plasmonic resonators arrays is achieved by virtue of the intrinsic properties to the constituent structures such as composition, size and shape and by controlling the inter-resonator interactions by of virtue the array geometrical arrangement. The nanoscale confinement of the plasmonic field enhances light-matter interactions enabling, for instance, the surface enhanced infrared absorption (SEIRA) effect. However, the subwavelength confinement also poses an experimental challenge for discriminating the response stemming from the individual resonators and from the collective response in densely packed arrays...
January 2016: ACS Photonics
Cyrille Hamon, Sergey M Novikov, Leonardo Scarabelli, Diego M Solís, Thomas Altantzis, Sara Bals, José M Taboada, Fernando Obelleiro, Luis M Liz-Marzán
Gold nanorod supercrystals have been widely employed for the detection of relevant bioanalytes with detection limits ranging from nano- to picomolar levels, confirming the promising nature of these structures for biosensing. Even though a relationship between the height of the supercrystal (i.e., the number of stacked nanorod layers) and the enhancement factor has been proposed, no systematic study has been reported. In order to tackle this problem, we prepared gold nanorod supercrystals with varying numbers of stacked layers and analyzed them extensively by atomic force microscopy, electron microscopy and surface enhanced Raman scattering...
October 21, 2015: ACS Photonics
Cynthia Vidal, Dong Wang, Peter Schaaf, Calin Hrelescu, Thomas A Klar
The search for novel plasmonic nanostructures, which can act simultaneously as optical detectors and stimulators, is crucial for many applications in the fields of biosensing, electro- and photocatalysis, electrochemistry, and biofuel generation. In most of these areas, a large surface-to-volume ratio, as well as high density of active surface sites, is desirable. We investigate sponge-like, that is, fully porous, nanoparticles, called nanosponges, where both the gold and the air phase are fully percolated in three dimensions...
October 21, 2015: ACS Photonics
Anton Hörl, Andreas Trügler, Ulrich Hohenester
Electron energy loss spectroscopy (EELS) has emerged as a powerful tool for the investigation of plasmonic nanoparticles, but the interpretation of EELS results in terms of optical quantities, such as the photonic local density of states, remains challenging. Recent work has demonstrated that, under restrictive assumptions, including the applicability of the quasistatic approximation and a plasmonic response governed by a single mode, one can rephrase EELS as a tomography scheme for the reconstruction of plasmonic eigenmodes...
October 21, 2015: ACS Photonics
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