Publications
795 results found
Liu C, Maier SA, 2022, High-Quality Optical Hotspots with Topology-Protected Robustness, ACS PHOTONICS, Vol: 9, Pages: 241-248, ISSN: 2330-4022
Aigner A, Dawes JM, Maier SA, et al., 2022, Nanophotonics shines light on hyperbolic metamaterials, LIGHT-SCIENCE & APPLICATIONS, Vol: 11, ISSN: 2047-7538
- Author Web Link
- Cite
- Citations: 13
Güsken NA, Fu M, Zapf M, et al., 2022, Fluorescence enhancement of Er<sup>3+</sup>-ions using reverse hybrid plasmonic nano-focusing
We report the broadband fluorescence enhancement of erbium ions embedded in a single non-resonant reverse nano-focusing waveguide. We measure a large radiative Purcell enhancement of a total emission rate enhancement of > 250 across the entire measured spectrum including the prominent telecoms C-band. Further, we observe the enhancement of single electric dipole transitions from Stark-split levels at room temperature.
Kühner L, Wendisch F, Maier SA, et al., 2022, Height-Driven Symmetry Breaking for High-Q Resonances in All-Dielectric Metasurfaces
We demonstrate a novel approach to control photonic bound states in the continuum induced by a symmetry-breaking with tailored resonator heights leading to more precisely engineered system asymmetries and new metasurface functionalities.
Kühner L, Wendisch F, Maier SA, et al., 2022, Height-Driven Symmetry Breaking for High-Q Resonances in All-Dielectric Metasurfaces
We demonstrate a novel approach to control photonic bound states in the continuum induced by a symmetry-breaking with tailored resonator heights leading to more precisely engineered system asymmetries and new metasurface functionalities.
Güsken NA, Fu M, Zapf M, et al., 2022, Fluorescence enhancement of Er<sup>3+</sup>-ions using reverse hybrid plasmonic nano-focusing
We report the broadband fluorescence enhancement of erbium ions embedded in a single non-resonant reverse nano-focusing waveguide. We measure a large radiative Purcell enhancement of a total emission rate enhancement of > 250 across the entire measured spectrum including the prominent telecoms C-band. Further, we observe the enhancement of single electric dipole transitions from Stark-split levels at room temperature.
Dinter T, Kühner L, Li C, et al., 2022, Metasurface measuring twisted light in turbulence
Practical free-space communication systems suffer from turbulence-induced phase distortions to propagating beams, destroying the orthogonality of orbital angular momentum (OAM) modes used for space-division multiplexing and introducing modal crosstalk. Here we present the design and use of an ultrathin OAM mode-sorting metasurface for investigating the deterioration of OAM orthogonality under different turbulence conditions, offering a compact, fast and efficient way to measure the OAM spectrum.
Tirole R, Vezzoli S, Galiffi E, et al., 2022, Single and double slit time diffraction at optical frequencies
In a temporal version of a single slit and Young's double slit experiments, newly generated optical frequencies form a diffraction pattern. The spectral extent of these frequencies is beyond the expected bandwidth of the modulation.
Boggiano HD, Nam L, Tilmann B, et al., 2022, Focusing a nano-earthquake
Plasmonic nanoantennas are optomechanical transducers for converting laser pulses into surface hypersound waves traveling through the underlying substrate, similar to the seismic waves after an earthquake. Here we introduce a novel design consisting of an array of plasmonic nanodisks allowing the focusing of the generated waves in the nanoscale.
Kim J, Bürger J, Schalles V, et al., 2022, The optofluidic 3D-nanoprinted hollow core micro-gap waveguide spectroscopy
We present a novel on-chip optofluidic hollow core micro-gap waveguide based on a strong light guidance through anti-resonant effect. We show gas and liquid-based spectroscopic experiments with simulations.
Aigner A, Wang J, Tittl A, et al., 2022, Out-of-plane symmetry-protected bound states in the continuum in a plasmonic nanofin metasurface
We present a plasmonic nanofin metasurface harnessing the out-of-plane symmetry breaking in parameter space by tuning the triangle angle of 3D laser nanoprinted polymer triangles (named as nanofins) coated with gold. The plasmonic nature of the out-of-plane symmetry-protected BICs enables high field enhancement together with high q-factors from the near- to mid-infrared regions, which were utilised for refractive index and pixelated molecular sensing.
Dinter T, Kühner L, Li C, et al., 2022, Metasurface measuring twisted light in turbulence
Practical free-space communication systems suffer from turbulence-induced phase distortions to propagating beams, destroying the orthogonality of orbital angular momentum (OAM) modes used for space-division multiplexing and introducing modal crosstalk. Here we present the design and use of an ultrathin OAM mode-sorting metasurface for investigating the deterioration of OAM orthogonality under different turbulence conditions, offering a compact, fast and efficient way to measure the OAM spectrum.
Aigner A, Wang J, Tittl A, et al., 2022, Out-of-plane symmetry-protected bound states in the continuum, Pages: 509-510
Symmetry-protected bound states in the continuum (BICs) combines high-quality factors (q-factors) with a large spectral tunability, offering an ideal platform for optical sensing. We present a plasmonic nanofin metasurface harnessing the out-of-plane symmetry breaking in parameter space by tuning the opening angle of 3D laser nanoprinted polymer triangles coated with gold. The plasmonic nature of the out-of-plane symmetry-protected BICs enables high surface field enhancement together with high q-factors, which have been utilised for refractive index and pixelated molecular sensing.
Li C, Schdmit MA, Maier SA, et al., 2022, All-on-fiber generation of higher-order Poincaré sphere beams via 3D lasernanoprinted metasurfaces, Pages: 1218-1219
We present a new metafiber platform for all-on-fiber polarization manipulation through implementing 3D laser-nanoprinted metasurfaces on the end face of polarizationmaintaining fibers. The unlocked height degree of freedom in 3D polymer meta-atoms eases the simultaneous polarization and phase control, leading to the generation of arbitrary higherorder Poincare sphere beams carrying different orbital angular momentum modes.
Kepič P, Ligmajer F, Hrtoň M, et al., 2022, Exploiting Mie resonances in VO2 nanoantennas for achieving optically tunable metasurfaces in the visible range, Pages: 680-681
We study the optical properties of VO2 nanodiscs in the visible range. These nanostructures present strong Mie resonances not only in the known high-temperature, plasmonic phase, but also in the low-temperature phase, in which the material’s behavior is predominantly dielectric. A large extinction modulation is observed when the nanodiscs go upon phase transition. The nanodiscs present large potential for being used as building blocks of a metasurface which can be tuned by shining a CW laser on it.
Schmidt MA, Schneidewind H, Hübner U, et al., 2022, Metasurfaces meet optical fibers: a novel platform for flexible optical trapping and boosting in-coupling efficiencies, Pages: 344-345
In this talk, we show that the combination of optical fibers with nanostructures defines a new class of fiber integrated devices — nanostructured fibers — which opensup new application areas for optical fiber research. Using 3D nanoprinting and modified electron beam lithography, we integrate high-NA meta-lenses and dielectric ring gratings onto the end faces of single-mode fibers. These devices enable efficient light coupling at angles up to 80° and trapping of Escherichia coli bacteria with an individual single-mode fiber device.
Sortino L, Maier SA, 2022, All-dielectric nanophotonics with quantum emitters in Transition Metal Dichalcogenides semiconductors
Transition metal dichalcogenides (TMDs) semiconductors offer a platform for merging nanophotonics and two-dimensional (2D) materials. They are exceptional quantum materials in the monolayer form and possess appealing optical properties as bulk materials, such as a high index of refraction and giant anisotropy. Here we show that the combination of monolayer TMDs and all-dielectric nanostructures, also made from bulk TMDs, provides new approaches for enhanced light-matter interaction of 2D excitons and quantum emitters with Mie-resonant nanophotonic devices.
Wendisch FJ, Bürger J, Gryb D, et al., 2022, Implementation of an optical setup for investigating chiral nanophotonic structures, Pages: 1110-1111
Chirality is inherent to Nature and happens on all scales from the fundamental biological building blocks up to the structure of galaxies. A pair of mirror-image molecules, called enantiomers, often give rise to tremendous differences in protein function, cell communication and organism health. The chirality of molecules is usually characterized via chiroptical effects using illumination with left and right circularly polarized light beams. However, due to the scale mismatch between the helical pitch of atoms in molecules and the wavelength of light, these chiroptical effects are inherently low and it remains challenging to sense and separate enantiomers. Recent advancements in nanophotonics offer solutions to overcome these limitations by enhancing chiral light-matter interactions by using chiral nanoparticles, metasurfaces or metamaterials. In this work, we report on the development of a setup dedicated to perform linear and nonlinear spectroscopy of chiral photonic nanostructures and on the investigation of the chiral behavior of selected nanophotonic platforms.
Gargiulo J, Barella M, Herran M, et al., 2022, In Situ optical thermometry of hybrid plasmonic nanosystems., Pages: 261-262
We present a new implementation of anti-Stokes thermometry that enables the in situ photothermal characterization of individual plasmonic nanoparticles from a single hyperspectral photoluminescence confocal image. We study the photothermal response at the single-particle level of spherical gold NPs with sizes ranging from 50 to 100 nm supported on glass, sapphire and graphene substrates. In addition, we study bimetallic Au@Pd NPs in a core@shell configuration. The developed method allows quantitative assessment of the role of temperature in plasmon-assisted applications.
Kühner L, Sortino L, Berté R, et al., 2022, Radial bound states in the continuum for polarization-invariant nanophotonics, Pages: 336-337
We demonstrate radial bound states in the continuum as a new concept for realizing resonances with high Q factors, strong near-field enhancements, and polarization invariance in a compact footprint, and utilize them for applications in biomolecular sensing and higher harmonic generation from 2D materials.
Aigner A, Wang J, Tittl A, et al., 2022, Out-of-plane symmetry-protected bound states in the continuum in a plasmonic nanofin metasurface
We present a plasmonic nanofin metasurface harnessing the out-of-plane symmetry breaking in parameter space by tuning the triangle angle of 3D laser nanoprinted polymer triangles (named as nanofins) coated with gold. The plasmonic nature of the out-of-plane symmetry-protected BICs enables high field enhancement together with high q-factors from the near- to mid-infrared regions, which were utilised for refractive index and pixelated molecular sensing.
Altug H, Oh S-H, Maier SA, et al., 2022, Advances and applications of nanophotonic biosensors, NATURE NANOTECHNOLOGY, Vol: 17, Pages: 5-16, ISSN: 1748-3387
- Author Web Link
- Cite
- Citations: 175
Büchner R, Weber T, Kühner L, et al., 2021, Tip coupling and array effects of gold nanoatennas in near-field microscopy, ACS Photonics, Vol: 8, Pages: 3486-3494, ISSN: 2330-4022
Scattering-type scanning near-field optical microscopy (s-SNOM) is one of the predominant techniques for the nanoscale characterization of optical properties. The optical response of nanoantennas in s-SNOM is highly sensitive to their environment, including influences of the probing tip or neighboring resonators. Dielectric tips are commonly employed to minimize tip-related perturbations, although they provide a comparatively weak scattering signal. Here we show that when using metallic tips, it is possible to select between distinct weak and strong tip–antenna coupling regimes by careful tailoring of the illumination conditions and resonator orientation. This enables the use of highly scattering metallic instead of dielectric tips for mapping plasmonic modes with comparatively higher signal strengths. This is a particular advantage for the retrieval of near-field spectra, which simultaneously require high near-field signals and unperturbed field patterns. We leverage our approach to analyze the collective effects of nanoantenna arrays, phenomena that are well understood in the optical far-field but have not been extensively studied in the near-field. Probing the dependence of the optical response on the array field size, we identify three regimes: the single rod regime, the intermediate regime, and the array-like regime. We show that these array effects give rise to characteristic spectral features originating from a complex interplay of radiative coupling and plasmon hybridization. These results provide evidence that long-range interactions of antennas also influence the local optical response that is probed in s-SNOM and demonstrate how collective resonances emerge from single building blocks, providing guidelines for optimized array designs for near- and far-field applications.
Moretti GQ, Cortes E, Maier SA, et al., 2021, Engineering gallium phosphide nanostructures for efficient nonlinear photonics and enhanced spectroscopies, Nanophotonics, Vol: 10, Pages: 4261-4271, ISSN: 2192-8606
Optical resonances arising from quasi-bound states in the continuum (QBICs) have been recently identified in nanostructured dielectrics, showing ultrahigh quality factors accompanied by very large electromagnetic field enhancements. In this work, we design a periodic array of gallium phosphide (GaP) elliptical cylinders supporting, concurrently, three spectrally separated QBIC resonances with in-plane magnetic dipole, out-of-plane magnetic dipole, and electric quadrupole characters. We numerically explore this system for second-harmonic generation and degenerate four-wave mixing, demonstrating giant per unit cell conversion efficiencies of up to ∼ 2 W−1 and ∼ 60 W−2, respectively, when considering realistic introduced asymmetries in the metasurface, compatible with current fabrication limitations. We find that this configuration outperforms by up to more than four orders of magnitude the response of low-Q Mie or anapole resonances in individual GaP nanoantennas with engineered nonlinear mode-matching conditions. Benefiting from the straight-oriented electric field of one of the examined high-Q resonances, we further propose a novel nanocavity design for enhanced spectroscopies by slotting the meta-atoms of the periodic array. We discover that the optical cavity sustains high-intensity fields homogeneously distributed inside the slot, delivering its best performance when the elliptical cylinders are cut from end to end forming a gap, which represents a convenient model for experimental investigations. When placing an electric point dipole inside the added aperture, we find that the metasurface offers ultrahigh radiative enhancements, exceeding the previously reported slotted dielectric nanodisk at the anapole excitation by more than two orders of magnitude.
Kuehne J, Wang J, Weber T, et al., 2021, Fabrication robustness in BIC metasurfaces, Nanophotonics, Vol: 10, Pages: 4305-4312, ISSN: 2192-8606
All-dielectric metasurfaces supporting photonic bound states in the continuum (BICs) are an exciting toolkit for achieving resonances with ultranarrow linewidths. However, the transition from theory to experimental realization can significantly reduce the optical performance of BIC-based nanophotonic systems, severely limiting their application potential. Here, we introduce a combined numerical/experimental methodology for predicting how unavoidable tolerances in nanofabrication such as random geometrical variations affect the performance of different BIC metasurface designs. We compare several established all-dielectric BIC unit cell geometries with broken in-plane inversion symmetry including tilted ellipses, asymmetric double rods, and split rings. Significantly, even for low fabrication-induced geometrical changes, both the BIC resonance amplitude and its quality factor (Q-factor) are significantly reduced. We find that the all-dielectric ellipses maintain the highest Q-factors throughout the geometrical variation range, whereas the rod and split ring geometries fall off more quickly. The same behavior is confirmed experimentally, where geometrical variation values are derived from automated processing of sets of scanning electron microscopy (SEM) images. Our methodology provides crucial insights into the performance degradation of BIC metasurfaces when moving from simulations to fabricated samples and will enable the development of robust, high-Q, and easy to manufacture nanophotonic platforms for applications ranging from biomolecular sensing to higher harmonic generation.
Luo S, Hoff BH, Maier SA, et al., 2021, Scalable Fabrication of Metallic Nanogaps at the Sub-10 nm Level, ADVANCED SCIENCE, Vol: 8
- Author Web Link
- Cite
- Citations: 24
Glass D, Quesada-Cabrera R, Bardey S, et al., 2021, Probing the role of atomic defects in photocatalytic systems through photoinduced enhanced raman scattering, ACS Energy Letters, Vol: 6, Pages: 4273-4281, ISSN: 2380-8195
Even in ultralow quantities, oxygen vacancies (VO) drastically impact keyproperties of metal oxide semiconductors, such as charge transport, surface adsorption,and reactivity, playing central roles in functional materials performance. Currentmethods used to investigate VO often rely on specialized instrumentation under far fromideal reaction conditions. Hence, the influence of VO generated in situ during catalyticprocesses has yet to be probed. In this work, we assess in situ extrinsic surface VOformation and lifetime under photocatalytic conditions which we compare tophotocatalytic performance. We show for the first time that lifetimes of in situ generatedatomic VO play more significant roles in catalysis than their concentration, with strongcorrelations between longer-lived VO and higher photocatalytic activity. Our resultsindicate that enhanced photocatalytic efficiency correlates with goldilocks VOconcentrations, where VO densities must be just right to encourage carrier transportwhile avoiding charge carrier trapping.
Huettenhofer L, Golibrzuch M, Bienek O, et al., 2021, Metasurface photoelectrodes for enhanced solar fuel generation, Advanced Energy Materials, Vol: 11, ISSN: 1614-6832
Tailoring optical properties in photocatalysts by nanostructuring them can help increase solar light harvesting efficiencies in a wide range of materials. Whereas plasmon resonances are widely employed in metallic catalysts for this purpose, latest advances of nonradiative, dielectric nanophotonics also enable light confinement and enhanced visible light absorption in semiconductors. Here, a design procedure for large-scale nanofabrication of semiconductor photoelectrodes using imprint lithography is developed. Anapole excitations and metasurface lattice resonances are combined to enhance the absorption of the model material, amorphous gallium phosphide (a-GaP), over the visible spectrum. It is shown that cost-effective, high sample throughput is achieved while retaining the precise signature of the engineered photonic states. Photoelectrochemical measurements under hydrogen evolution reaction conditions and sunlight illumination reveal the contributions of the respective resonances and demonstrate an overall photocurrent enhancement of 5.7, compared to a planar film. These results are supported by optical and numerical analysis of single nanodisks and of the upscaled metasurface.https://onlinelibrary.wiley.com/doi/10.1002/aenm.202102877
Poblet M, Berte R, Boggiano HD, et al., 2021, Acoustic coupling between plasmonic nanoantennas: detection and directionality of surface acoustic waves, ACS Photonics, Vol: 8, Pages: 2846-2852, ISSN: 2330-4022
Hypersound waves can be efficient mediators between optical signals at the nanoscale. Having phase velocities several orders of magnitude lower than the speed of light, they propagate with much shorter wavelengths and can be controlled, directed, and even focused in a very small region of space. This work shows how two optical nanoantennas can be coupled through an acoustic wave that propagates with a certain directionality. An “emitter” antenna is first optically excited to generate acoustic coherent phonons that launch surface acoustic waves through the underlying substrate. These waves travel until they are mechanically detected by a “receiver” nanoantenna whose oscillation produces a detectable optical signal. Generation and detection are studied in detail, and new designs are proposed to improve the directionality of the hypersonic surface acoustic wave.
Sortino L, Zotev PG, Phillips CL, et al., 2021, Bright single photon emitters with enhanced quantum efficiency in a two-dimensional semiconductor coupled with dielectric nano-antennas, Nature Communications, Vol: 12, ISSN: 2041-1723
Single photon emitters in atomically-thin semiconductors can be deterministically positioned using strain induced by underlying nano-structures. Here, we couple monolayer WSe2 to high-refractive-index gallium phosphide dielectric nano-antennas providing both optical enhancement and monolayer deformation. For single photon emitters formed on such nano-antennas, we find very low (femto-Joule) saturation pulse energies and up to 104 times brighter photoluminescence than in WSe2 placed on low-refractive-index SiO2 pillars. We show that the key to these observations is the increase on average by a factor of 5 of the quantum efficiency of the emitters coupled to the nano-antennas. This further allows us to gain new insights into their photoluminescence dynamics, revealing the roles of the dark exciton reservoir and Auger processes. We also find that the coherence time of such emitters is limited by intrinsic dephasing processes. Our work establishes dielectric nano-antennas as a platform for high-efficiency quantum light generation in monolayer semiconductors.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.