Publications
799 results found
Grinblat G, Zhang H, Nielsen MP, et al., 2020, Efficient ultrafast all-optical modulation in a nonlinear crystalline gallium phosphide nanodisk at the anapole excitation, Science Advances, Vol: 6, ISSN: 2375-2548
High–refractive index nanostructured dielectrics have the ability to locally enhance electromagnetic fields with low losses while presenting high third-order nonlinearities. In this work, we exploit these characteristics to achieve efficient ultrafast all-optical modulation in a crystalline gallium phosphide (GaP) nanoantenna through the optical Kerr effect (OKE) and two-photon absorption (TPA) in the visible/near-infrared range. We show that an individual GaP nanodisk can yield differential reflectivity modulations of up to ~40%, with characteristic modulation times between 14 and 66 fs, when probed at the anapole excitation (AE). Numerical simulations reveal that the AE represents a unique condition where both the OKE and TPA contribute with the same modulation sign, maximizing the response. These findings highly outperform previous reports on sub–100-fs all-optical switching from resonant nanoscale dielectrics, which have demonstrated modulation depths no larger than 0.5%, placing GaP nanoantennas as a promising choice for ultrafast all-optical modulation at the nanometer scale.
Danesh M, Zadeh MJ, Zhang T, et al., 2020, Monolayer Conveyor for Stably Trapping and Transporting Sub-1 nm Particles, LASER & PHOTONICS REVIEWS, Vol: 14, ISSN: 1863-8880
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- Citations: 14
Mancini A, Gubbin CR, Berte R, et al., 2020, Near-Field Spectroscopy of Cylindrical Phonon-Polariton Antennas, ACS NANO, Vol: 14, Pages: 8508-8517, ISSN: 1936-0851
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- Citations: 10
Kalinic B, Cesca T, Mignuzzi S, et al., 2020, All-dielectric silicon nanoslots for Er3+ photoluminescence enhancement, Physical Review Applied, Vol: 14, Pages: 014086 – 1-014086 – 11, ISSN: 2331-7019
We study, both experimentally and theoretically, the modification of Er3+ photoluminescence properties in Si dielectric nanoslots. The ultrathin nanoslot (down to 5-nm thickness), filled with Er in SiO2, boosts the electric and magnetic local density of states via coherent near-field interaction. We report an experimental 20-fold enhancement of the radiative decay rate with negligible losses. Moreover, via modifying the geometry of the all-dielectric nanoslot, the outcoupling of the emitted radiation to the far field can be strongly improved, without affecting the strong decay-rate enhancement given by the nanoslot structure. Indeed, for a periodic square array of slotted nanopillars an almost one-order-of-magnitude-higher Er3+ PL intensity is measured with respect to the unpatterned structures. This has a direct impact on the design of more efficient CMOS-compatible light sources operating at telecom wavelengths.
Liu C, Maier SA, Li G, 2020, Genetic-Algorithm-Aided Meta-Atom Multiplication for Improved Absorption and Coloration in Nanophotonics, ACS PHOTONICS, Vol: 7, Pages: 1716-1722, ISSN: 2330-4022
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- Citations: 29
Boggiano HD, Berte R, Scarpettini AF, et al., 2020, Determination of nanoscale mechanical properties of polymers via plasmonic nanoantennas, ACS Photonics, Vol: 7, Pages: 1403-1409, ISSN: 2330-4022
Nanotechnology and the consequent emergence of miniaturized devices are driving the need to improve our understanding of the mechanical properties of a myriad of materials. Here we focus on amorphous polymeric materials and introduce a new way to determine the nanoscale mechanical response of polymeric thin films in the GHz range, using ultrafast optical means. Coupling of the films to plasmonic nanoantennas excited at their vibrational eigenfrequencies allows the extraction of the values of the mechanical moduli as well as the estimation of the glass transition temperature via time-domain measurements, here demonstrated for PMMA films. This nanoscale method can be extended to the determination of mechanical and elastic properties of a wide range of spatially strongly confined materials.
Gusken NA, Nielsen MP, Nguyen NB, et al., 2020, Efficient Four Wave Mixing and Low-Loss Adiabatic In-Coupling in Hybrid Gap Plasmonic Waveguides, ISSN: 1092-8081
We show four-wave-mixing over 2 μm with 1% signal-to-idler conversion efficiency enabled by strong non-linearities and highly confined fields. We also demonstrate low-loss in-coupling into nanometer gaps with an efficiency of 80%.
Doiron B, Gusken NA, Lauri A, et al., 2020, Hot Carrier Optoelectronics with Titanium Nitride, Lasers and Electro-Optics Society Annual Meeting-LEOS, ISSN: 1092-8081
© 2020 OSA. Titanium oxynitride enables a range of plasmonic and optoelectronic functionality using long-lived photo-generated hot carriers. We explore the time scale of hot carriers in TiN and their use in photochemical reduction and Schottky detectors.
Mao P, Liu C, Song F, et al., 2020, Manipulating disordered plasmonic systems by external cavity with transition from broadband absorption to reconfigurable reflection, NATURE COMMUNICATIONS, Vol: 11, ISSN: 2041-1723
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- Citations: 50
Morozov S, Pensa EL, Khan AH, et al., 2020, Electrical control of single-photon emission in highly-charged individual colloidal quantum dots, Publisher: arXiv
Electron transfer to an individual quantum dot promotes the formation ofcharged excitons with enhanced recombination pathways and reduced lifetimes.Excitons with only one or two extra charges have allowed for the development ofvery efficient quantum dot lasing [1] and the understanding of blinkingdynamics [2], while charge transfer management has yielded single quantum dotLEDs [3], LEDs with reduced efficiency roll-off [4], and enabled studies ofcarrier and spin dynamics [5]. Here, by room-temperature time-resolvedexperiments on individual giant-shell CdSe/CdS quantum dots, we show theelectrochemical formation of highly charged excitons containing more thantwelve electrons and one hole. We report control of intensity blinking, as wellas a deterministic manipulation of quantum dot photodynamics, with an observed210-fold increase of the decay rate, accompanied by 12-fold decrease of theemission intensity, all while preserving single-photon emissioncharacteristics. These results pave the way for deterministic control over thecharge state, and room-temperature decay-rate engineering for colloidal quantumdot-based classical and quantum communication technologies.
Proctor M, Huidobro PA, Maier SA, et al., 2020, Manipulating topological valley modes in plasmonic metasurfaces, Nanophotonics, Vol: 9, Pages: 657-665, ISSN: 2192-8606
The coupled light-matter modes supported by plasmonic metasurfaces can be combined with topological principles to yield subwavelength topological valley states of light. We give a systematic presentation of the topological valley states available for lattices of metallic nanoparticles: All possible lattices with hexagonal symmetry are considered, as well as valley states emerging on a square lattice. Several unique effects which have yet to be explored in plasmonics are identified, such as robust guiding, filtering and splitting of modes, as well as dual-band effects. We demonstrate these by means of scattering computations based on the coupled dipole method that encompass the full electromagnetic interactions between nanoparticles.
Sortino L, Brooks M, Zotev PG, et al., 2020, Dielectric nano-antennas for strain engineering in atomically thin two-dimensional semiconductors, Publisher: arXiv
Atomically thin two-dimensional semiconducting transition metaldichalcogenides (TMDs) can withstand large levels of strain before theirirreversible damage occurs. This unique property offers a promising route forcontrol of the optical and electronic properties of TMDs, for instance bydepositing them on nano-structured surfaces, where position-dependent straincan be produced on the nano-scale. Here, we demonstrate strain-inducedmodifications of the optical properties of mono- and bilayer TMD WSe$_2 $placed on photonic nano-antennas made from gallium phosphide (GaP).Photoluminescence (PL) from the strained areas of the TMD layer is enhancedowing to the efficient coupling with the confined optical mode of thenano-antenna. Thus, by following the shift of the PL peak, we deduce thechanges in the strain in WSe$_2$ deposited on the nano-antennas of differentradii. In agreement with the presented theory, strain up to $\approx 1.4 \%$ isobserved for WSe$_2$ monolayers. We also estimate that $>3\%$ strain isachieved in bilayers, accompanied with the emergence of a direct bandgap inthis normally indirect-bandgap semiconductor. At cryogenic temperatures, wefind evidence of the exciton confinement in the most strained nano-scale partsof the WSe$_2$ layers, as also predicted by our theoretical model. Our results,of direct relevance for both dielectric and plasmonic nano-antennas, show thatstrain in atomically thin semiconductors can be used as an additional parameterfor engineering light-matter interaction in nano-photonic devices.
Hüttenhofer L, Eckmann F, Lauri A, et al., 2020, Anapole excitations in oxygen vacancy-rich TiO2-x nanoresonators: tuning the absorption for photocatalysis in the visible., ACS Nano, Vol: 14, Pages: 2456-2464, ISSN: 1936-0851
Research on optically resonant dielectric nanostructures has accelerated the development of photonic applications, driven by their ability to strongly confine light on the nanoscale. However, since dielectric resonators are typically operated below their bandgap to minimize optical losses, the usage of dielectric nanoantenna concepts for absorption enhancement has largely remained unexplored. In this work, we realize engineered nanoantennas composed of photocatalytic dielectrics and demonstrate their increased light harvesting capabilities in otherwise weakly absorptive spectral regions. In particular, we employ anapole excitations, which are known for their strong light confinement, in nanodisks of oxygen-vacancy-rich TiO2-x, a prominent photocatalyst that provides a powerful platform for exploring concepts in absorption enhancement in tunable nanostructures. We show that by varying the nanodisk geometry, we can shift the anapole wavelength into resonance with optical transitions associated with the sub-bandgap oxygen vacancy (VO) states and thereby increase visible light absorption. The arising photocatalytic effect is monitored on the single particle level using the well-established photocatalytic silver reduction reaction on TiO2. With the freedom of changing the optical properties of TiO2 through tuning the abundance of VO-states we discuss the interplay between cavity damping and the anapole-assisted field confinement for absorption enhancement. This concept is general and can be extended to other catalytic materials with higher refractive indices.
Mao P, Liu C, Chen Q, et al., 2020, Broadband SERS detection with disordered plasmonic hybrid aggregates, NANOSCALE, Vol: 12, Pages: 93-102, ISSN: 2040-3364
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- Citations: 30
Doiron B, Güsken NA, Lauri A, et al., 2020, Hot carrier optoelectronics with titanium nitride
Titanium oxynitride enables a range of plasmonic and optoelectronic functionality using long-lived photo-generated hot carriers. We explore the time scale of hot carriers in TiN and their use in photochemical reduction and Schottky detectors.
Gennaro SD, Li Y, Maier SA, et al., 2020, Mixed order nonlinear processes from metasurfaces of multi-resonant gold antennas
We demonstrate mixed-order nonlinear frequency mixing in Au antennas and reveal the role of high order antenna modes in Pancharatnam-Berry Phase metasurfaces. The application of ultrafast pulse characterization is explored.
Gennaro SD, Li Y, Maier SA, et al., 2020, Nonlinear geometric phase gradient metasurfaces beyond the dipole approximation
In this work, we identify the role of higher order antenna’s modes on a metasurface’s Pancharatnam – Berry phase by investigating second harmonic light scattering from two metasurfaces exhibiting dipolar and quadrupolar radiation.
Gusken NA, Lauri A, Li Y, et al., 2020, IR hot carrier based photodetection in titanium nitride oxide thin film-Si junctions, MRS Advances, Vol: 5, Pages: 1843-1850, ISSN: 2059-8521
Hot carrier based methods constitute a valuable approach for efficient and silicon compatible sub-bandgap photodetection. Although, hot electron excitation and transfer have been studied extensively on traditional materials such as Au and Ti, reports on alternative materials such as titanium nitride (TiN) are rare. Here, we perform hot hole photodetection measurements on a p-Si/metal thin film junction using Ti, Au and TiN. This material is of interest as it constitutes a refractory alternative to Au which is an important property for plasmonic applications where high field intensities can occur. In contrast to Au, a TiN/Si junction does not suffer from metal diffusion into the Si, which eases the integration with current Si-fabrication techniques. This work shows that a backside illuminated p-Si/TiN system can be used for efficient hot hole extraction in the IR, allowing for a responsivity of 1 mA/W at an excitation wavelength of 1250 nm and at zero bias. Via a comparison between TiN and other commonly used materials such as Au, the origin of this comparably high photoresponse can be traced back to be directly linked to a thin TiO2-x interfacial layer allowing for a distinct hot-hole transfer mechanism. Moreover, the fabrication of TiN nanodisk arrays is demonstrated which bears great promise to further boost the device efficiency.
Jang B, Gargiulo J, Ziegler M, et al., 2020, Fine-tuning of the optical properties of hollow-core light cages using dielectric nanofilms, Optics Letters, Vol: 45, Pages: 196-199, ISSN: 0146-9592
Here, we show that the optical properties of direct-laser-written on-chip hollow-core waveguides—so-called light cages—can be controlled to a very high degree by dielectric nanofilms. Using low-temperature atomic layer deposition (ALD), alumina nanofilms are concentrically deposited on the high-aspect strands that surround the central air core and confine the light via the anti-resonant effect. In accordance with modal cutoff simulations without any free parameters, a linear spectral shift of the resonances with increasing film thickness is experimentally observed. The phenomenon is explained by a shift in the dispersions of cladding supermodes. As neither cage geometry nor polymer is affected by the film deposition, our results suggest ALD to be an essential tool for fine-tuning the properties of hollow-core light cages and to protect them from aggressive substances, being relevant for, e.g., bioanalytics or quantum technology.
Langer J, de Aberasturi DJ, Aizpurua J, et al., 2020, Present and Future of Surface-Enhanced Raman Scattering, ACS NANO, Vol: 14, Pages: 28-117, ISSN: 1936-0851
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- Citations: 1720
Gennaro SD, Li Y, Maier SA, et al., 2020, Mixed order nonlinear processes from metasurfaces of multi-resonant gold antennas, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020
Glass D, Cortes E, Peveler WJ, et al., 2020, Enhancing hybrid metal-semiconductor systems beyond SERS with PIERS (Photo-induced enhanced Raman scattering) for trace analyte detection, Conference on Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXI held at SPIE Defense + Commercial Sensing Conference, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
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- Citations: 1
Zaza C, Violi IL, Gargiulo J, et al., 2020, Size-selective optical printing of silicon nanoparticles through their dipolar magnetic resonance, Conference on Complex Light and Optical Forces XIV, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Gusken NA, Nielsen MP, Nguyen NB, et al., 2020, Efficient four wave mixing and low-loss adiabatic in-coupling in hybrid gap plasmonic waveguides, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020
Ren H, Maier SA, 2020, Complex-amplitude metasurfaces for orbital angular momentum multiplexing holography, Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR), Publisher: IEEE
Rakovich A, Po S, do Carmo MP, et al., 2020, Nanophotonic approaches to biosensing applications, International Conference on Laser Optics (ICLO), Publisher: IEEE
Po S, Carmo MP, Zhao M, et al., 2020, Hybrid plasmonic-SERS based biosensing, International Conference on Laser Optics (ICLO), Publisher: IEEE
Gennaro SD, Li Y, Maier SA, et al., 2020, Nonlinear Geometric Phase Gradient Metasurface beyond the Dipole Approximation, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020
Glass D, Cortes E, Ben-Jaber S, et al., 2019, Dynamics of Photo-Induced Surface Oxygen Vacancies in Metal-Oxide Semiconductors Studied Under Ambient Conditions, ADVANCED SCIENCE, Vol: 6
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- Citations: 64
Sortina L, Zotev PG, Mignuzzi S, et al., 2019, Enhanced light-matter interaction in an atomically thin semiconductor coupled with dielectric nano-antennas, Nature Communications, Vol: 50, Pages: 1-8, ISSN: 2041-1723
Unique structural and optical properties of atomically thin transition metal dichalcogenides (TMDs) enable in principle their efficient coupling to photonic cavities having the optical mode volume below the diffraction limit. So far, this has only been demonstrated by coupling TMDs with plasmonic modes in metallic nano-structures, which exhibit strong energy dissipation limiting their potential applications in devices. Here, we present an alternative approach for realisation of ultra-compact cavities interacting with two-dimensional semiconductors: we use mono- and bilayer TMD WSe2 coupled to low-loss high-refractive-index gallium phosphide (GaP) nano-antennas. We observe a photoluminescence (PL) enhancement exceeding 104 compared with WSe2 placed on the planar GaP, and trace its origin to a combination of enhancement of the spontaneous light emission rate, favourable modification of the PL directionality and enhanced optical excitation efficiency, all occurring as a result of WSe2 coupling with strongly confined photonic modes of the nano-antennas. Further effect of the coupling is observed in the polarisation dependence of WSe2 PL, and in the Raman scattering signal enhancement exceeding 103. Our findings reveal high-index dielectric nano-structures as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
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