40 research outputs found
Multi-mode lasing in supercell plasmonic nanoparticle arrays
Multicolour light sources can be used in applications such as lighting and
multiplexing signals. In photonic and plasmonic systems, one way to achieve
multicolour light is via multi-mode lasing. To achieve this, plasmonic
nanoparticle arrays are typically arranged in superlattices that lead to
multiple dispersions of the single arrays coupled via the superlattice Bragg
modes. Here, we show an alternative way to enable multi-mode lasing in
plasmonic nanoparticle arrays. We design a supercell in a square lattice by
leaving part of the lattice sites empty. This results in multiple dispersive
branches caused by the supercell period and hence creates additional band edges
that can support lasing. We experimentally demonstrate multi-mode lasing in
such a supercell array. Furthermore, we identify the lasing modes by
calculating the dispersion by combining the structure factor of the array
design with an empty lattice approximation. We conclude that the lasing modes
are the 74th - and 106th -point of the supercell. By tuning the
square lattice period with respect to the gain emission we can control the
modes that lase. Finally, we show that the lasing modes exhibit a combination
of transverse electric and transverse magnetic mode characteristics in
polarization resolved measurements
Molecular coupling of light with plasmonic waveguides
We use molecules to couple light into and out of microscale plasmonic
waveguides. Energy transfer, mediated by surface plasmons, from donor molecules
to acceptor molecules over ten micrometer distances is demonstrated. Also
surface plasmon coupled emission from the donor molecules is observed at
similar distances away from the excitation spot. The lithographic fabrication
method we use for positioning the dye molecules allows scaling to nanometer
dimensions. The use of molecules as couplers between far-field and near-field
light offers the advantages that no special excitation geometry is needed, any
light source can be used to excite plasmons and the excitation can be localized
below the diffraction limit. Moreover, the use of molecules has the potential
for integration with molecular electronics and for the use of molecular
self-assembly in fabrication. Our results constitute a proof-of-principle
demonstration of a plasmonic waveguide where signal in- and outcoupling is done
by molecules.Comment: 9 pages, 5 figure
Raman Enhancement in Bowtie-Shaped Aperture-Particle Hybrid Nanostructures Fabricated with DNA-Assisted Lithography
We report on efficient surface-enhanced Raman spectroscopy (SERS) supporting
substrates, which are based on DNA-assisted lithography (DALI) and a layered
configuration of materials. In detail, we used nanoscopic DNA origami bowtie
templates to form hybrid nanostructures consisting of aligned silver
bowtie-shaped particles and apertures of similar shape in a silver film. We
hypothesized that this particular geometry could facilitate a four-fold
advantage in Raman enhancement compared to common particle-based SERS
substrates, and further, we verified these hypotheses experimentally and by
finite difference time domain simulations. In summary, our DALI-fabricated
hybrid structures suppress the background emission, allow emission
predominantly from the areas of high field enhancement, and support additional
resonances associated with the nanoscopic apertures. Finally, these
nanoapertures also enhance the fields associated with the resonances of the
underlying bowtie particles. The versatility and parallel nature of our DNA
origami-based nanofabrication scheme and all of the above-mentioned features of
the hybrid structures therefore make our optically resonant substrates
attractive for various SERS-based applications.Comment: 7 pages, 4 figures, Supporting Information (5 pages, 3 tables, 1
figure
Single-shot measurement of overall degree of spectral coherence : Bulk-generated supercontinuum case
Spectral and temporal correlations determine the majority of pulse properties, and a high degree of coherence is needed for minimizing the pulse length. However, there is no simple way to quantify these correlations experimentally, and nonlinear methods are often required. In this paper, we confirm an earlier proposed experiment [Koivurova, Opt. Lett. 44, 522 (2019)]0146-959210.1364/OL.44.000522 that can accurately estimate the spectral degree of coherence of arbitrary nonstationary fields. The method is entirely linear and can retrieve the quasicoherent contribution of the spectral correlation function. In particular, the method can be used to measure the overall degree of spectral coherence in a single-shot manner. We first establish the theoretical framework behind the method and experimentally test it for a bulk-generated supercontinuum. Our experimental results are in good agreement with the theory and confirm our earlier numerical findings [Halder, Photon. Res. 7, 1345 (2019)]2327-912510.1364/PRJ.7.001345. Moreover, the results yield insight into supercontinuum generation in bulk material.acceptedVersionPeer reviewe
Thermal Control of Plasmonic Surface Lattice Resonances
Plasmonic metasurfaces exhibiting collective responses known as surface
lattice resonances (SLRs) show potential for realizing tunable and flat
photonic components for wavelength-selective processes, including lasing and
optical nonlinearities. However, post-fabrication tuning of SLRs remains
challenging, limiting the applicability of SLR-based components. Here, we
demonstrate how the properties of high quality factor SLRs are easily modified
by breaking the symmetry of the nanoparticle surroundings. We break the
symmetry by changing the refractive index of the overlying immersion oil simply
by controlling the ambient temperature of the device. We show that already
modest temperature changes of 10{\deg}C can increase the quality factor of the
investigated SLR from 400 to 750. Our results demonstrate accurate and
reversible modification of the properties of the SLRs, paving the way towards
tunable SLR-based photonic devices. On a more general level, our results
demonstrate how symmetry breaking of the surrounding dielectric environment can
be utilized for efficient and potentially ultrafast modification of the SLR
properties
Phase-Matched Second-Harmonic Generation from Metasurfaces Inside Multipass Cells
We demonstrate a simple and scalable approach to increase conversion
efficiencies of nonlinear metasurfaces by incorporating them into multipass
cells and by letting the pump beam to interact with the metasurfaces multiple
times. We experimentally show that by metasurface design, the associated
phase-matching criteria can be fulfilled. As a proof of principle, we achieve
phase matching of second-harmonic generation (SHG) using a metasurface
consisting of aluminium nanoparticles deposited on a glass substrate. The
phase-matching condition is verified to be achieved by measuring superlinear
dependence of the detected SHG as a function of number of passes. We measure an
order of magnitude enhancement in the SHG signal when the incident pump
traverses the metasurface up to 9 passes. Results are found to agree well with
a simple model developed to estimate the generated SHG signals. We also discuss
strategies to further scale-up the nonlinear signal generation. Our approach
provides a clear pathway to enhance nonlinear optical responses of
metasurface-based devices. The generic nature of our approach holds promise for
diverse applications in nonlinear optics and photonics
Nonlinear nonlocal metasurfaces
Optical metasurfaces have recently emerged as the game changer in light manipulation and opened up new perspectives in many subfields of optics and photonics. Recent developments in nonlocal metasurfaces, in which the nanoscale building blocks respond to the incoming light collectively rather than as individual objects, are especially promising for enhancing and controlling the nonlinear optical phenomena. In this article, we provide a brief overview of the basic principles of nonlocal metasurfaces in the context of their nonlinear optical functionalities. We discuss the origin and the regimes of the nonlocal response, covering the aspects of multiple scattering, radiation damping, quality factor, local-field enhancement, and temporal dynamics. Some important aspects are illustrated by computational examples. We also give our personal viewpoint on the selected ideas and research directions in nonlocal and nonlinear metasurfaces, including the role of spatial symmetry in nonlocal interactions, the effects of phase and momentum matching in frequency conversion, as well as the possibilities offered by new material platforms and novel concepts, such as bound states in the continuum, parity-time symmetry, and time-variant metasurfaces.publishedVersionPeer reviewe
Scattering dominated spatial coherence and phase correlation properties in plasmonic lattice lasers
We present a comprehensive study of the polarization and spatial coherence properties of the lasing modes supported by a four-fold symmetric plasmonic lattice. We can distinguish the scattering induced effects from the lattice geometry induced effects by modifying only the diameter of the particles while keeping the lattice geometry constant. Customized interferometric measurements reveal that the lasing emission undergoes a drastic change from 1D to 2D spatial coherence with increasing particle size, accompanied with dramatic changes in the far field polarization and beaming properties. By utilizing T-matrix scattering simulations, we reveal the physical mechanism governing this transition. In particular, we find that there exists increased radiative coupling in the diagonal directions at the plane of the lattice when the particle diameter is increased. Finally, we demonstrate that the x- and y-polarized (degenerate) lasing modes become phase locked with sufficiently large particles.publishedVersionPeer reviewe
Influence of enzyme immobilization and skin-sensor interface on non-invasive glucose determination from interstitial fluid obtained by magnetohydrodynamic extraction
We integrated a magnetohydrodynamic fluid extractor with an amperometric glucose biosensor to develop a wearable device for non-invasive glucose monitoring. Reproducible fluid extraction through the skin and efficient transport of the extracted fluid to the biosensor surface are prerequisites for non-invasive glucose monitoring. We optimized the enzyme immobilization and the interface layer between the sensing device and the skin. The monitoring device was evaluated by extracting fluid through porcine skin followed by glucose detection at the biosensor. The biosensor featured a screen-printed layer of Prussian Blue that was coated with a layer containing glucose oxidase. Both physical entrapment of glucose oxidase in chitosan and tethering of glucose oxidase to electrospun nanofibers were evaluated. Binding of glucose oxidase to nanofibers under mild conditions provided a stable biosensor with analytical performance suitable for accurate detection of micromolar concentrations of glucose. Hydrogels of varying thickness (95-2000 mu m) as well as a thin (30 mu m) nanofibrous polycaprolactone mat were studied as an interface layer between the biosensor and the skin. The effect of mass transfer phenomena at the biosensor-skin interface on the analytical performance of the biosensor was evaluated. The sensing device detected glucose extracted through porcine skin with an apparent (overall) sensitivity of-0.8 mA/(M.cm(2)), compared to a sensitivity of-17 mA/(M.cm(2)) for measurement in solution. The amperometric response of the biosensor correlated with the glucose concentration in the fluid that had been extracted through porcine skin with the magnetohydrodynamic technique.Peer reviewe
Strong coupling between surface plasmon polaritons and Sulforhodamine 101 dye
We demonstrate a strong coupling between surface plasmon polaritons and Sulforhodamine 101 dye molecules. Dispersion curves for surface plasmon polaritons on samples with a thin layer of silver covered with Sulforhodamine 101 molecules embedded in SU-8 polymer are obtained experimentally by reflectometry measurements and compared to the dispersion of samples without molecules. Clear Rabi splittings, with energies up to 360 and 190 meV, are observed at the positions of the dye absorption maxima. The split energies are dependent on the number of Sulforhodamine 101 molecules involved in the coupling process. Transfer matrix and coupled oscillator methods are used to model the studied multilayer structures with a great agreement with the experiments. Detection of the scattered radiation after the propagation provides another way to obtain the dispersion relation of the surface plasmon polaritons and, thus, provides insight into dynamics of the surface plasmon polariton/dye interaction, beyond the refrectometry measurements