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Plasmonic Diamond Membranes for Ultrafast Silicon Vacancy Emission. NANO LETTERS 2024; 24:3575-3580. [PMID: 38478720 PMCID: PMC10979444 DOI: 10.1021/acs.nanolett.3c04002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 02/16/2024] [Accepted: 02/20/2024] [Indexed: 03/28/2024]
Abstract
Silicon vacancy centers (SiVs) in diamond have emerged as a promising platform for quantum sciences due to their excellent photostability, minimal spectral diffusion, and substantial zero-phonon line emission. However, enhancing their slow nanosecond excited-state lifetime by coupling to optical cavities remains an outstanding challenge, as current demonstrations are limited to ∼10-fold. Here, we couple negatively charged SiVs to sub-diffraction-limited plasmonic cavities and achieve an instrument-limited ≤8 ps lifetime, corresponding to a 135-fold spontaneous emission rate enhancement and a 19-fold photoluminescence enhancement. Nanoparticles are printed on ultrathin diamond membranes on gold films which create arrays of plasmonic nanogap cavities with ultrasmall volumes. SiVs implanted at 5 and 10 nm depths are examined to elucidate surface effects on their lifetime and brightness. The interplay between cavity, implantation depth, and ultrathin diamond membranes provides insights into generating ultrafast, bright SiV emission for next-generation diamond devices.
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2
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Uncovering the Mechanisms of Triplet-Triplet Annihilation Upconversion Enhancement via Plasmonic Nanocavity Tuning. ACS NANO 2023. [PMID: 38014847 DOI: 10.1021/acsnano.3c08915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The nonlinear conversion of photons from lower to higher energy is important for a wide range of applications, from quantum communications and optoelectronics to solar energy conversion and medicine. Triplet-triplet annihilation upconversion (TTA UC), which utilizes an absorber/emitter molecular pair, is a promising tool for upconversion applications requiring low intensity light such as photovoltaics, photocatalysis, and bioimaging. Despite demonstrations of efficient TTA UC in solution, practical applications have proven difficult, as thin films retard the necessary energy transfer steps and result in low emission yields. In this work, TTA UC emission from a thin film is greatly enhanced through integration into plasmonic nanogap cavities consisting of a silver mirror, a nanometer-scale polymer spacer containing a TTA molecular pair, and colloidally synthesized silver nanocubes. Mechanistic studies performed by varying the nanocube side length (45-150 nm) to tune the nanogap cavity resonance paired with simulations reveal absorption rate enhancement to be the primary operative mechanism in overall TTA UC emission enhancement. This absorption enhancement decreases the TTA UC threshold intensity by an order of magnitude and allows TTA UC emission to be excited with light up to 120 nm redder than the usable wavelength range for the control samples. Further, combined nanogap cavities composed of two distinct nanocube sizes result in surfaces which simultaneously enhance the absorption rate and emission rate. These dual-size nanogap cavities result in 45-fold TTA UC emission enhancement. In total, these studies present TTA UC emission enhancement, illustrate how the usable portion of the spectrum can be expanded for a given sensitizer-emitter pair, and develop both mechanistic understanding and design rules for TTA UC emission enhancement by plasmonic nanostructures.
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3
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Tracking light-induced charge transport. Science 2023; 382:264-265. [PMID: 37856583 DOI: 10.1126/science.adk6862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
Precise charge dynamics could help to improve the operation of solar cells and sensors.
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Ultrathin Pyroelectric Photodetector with Integrated Polarization-Sensing Metasurface. NANO LETTERS 2023; 23:8547-8552. [PMID: 37671730 DOI: 10.1021/acs.nanolett.3c02341] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
An abundance of metallic metasurfaces have been realized with miniscule, intricate features capable of tailored scattering, reflection, and absorption; however, high losses through heat limit their use in optoelectronics. Here, codesign of a detector and a polarization-sensing metasurface overcomes this challenge by utilizing the heat generation for integrated pyroelectric detection of the incoming light polarization. Using a nanogap metasurface with asymmetric metallic elements, polarization-sensitive photodetection exhibits high extinction ratios up to 19 for orthogonally polarized light and allows extraction of Stokes parameters with <12% deviation from theoretical values. This polarization-sensitive photodetector is ultrathin, consisting of active layers of only 290 nm, and exhibits fast response times of ∼2 ns. The structure is fully integrated, requiring no external cameras, detectors, or power sources, and points toward the creation of layered, multifunctional devices that utilize exotic metasurface properties for novel and compact sensing and imaging.
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5
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Plasmonic Fluorescence Enhancement in Diagnostics for Clinical Tests at Point-of-Care: A Review of Recent Technologies. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2107986. [PMID: 35332957 PMCID: PMC9986847 DOI: 10.1002/adma.202107986] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 01/26/2022] [Indexed: 05/31/2023]
Abstract
Fluorescence-based biosensors have widely been used in the life-sciences and biomedical applications due to their low limit of detection and a diverse selection of fluorophores that enable simultaneous measurements of multiple biomarkers. Recent research effort has been made to implement fluorescent biosensors into the exploding field of point-of-care testing (POCT), which uses cost-effective strategies for rapid and affordable diagnostic testing. However, fluorescence-based assays often suffer from their feeble signal at low analyte concentrations, which often requires sophisticated, costly, and bulky instrumentation to maintain high detection sensitivity. Metal- and metal oxide-based nanostructures offer a simple solution to increase the output signal from fluorescent biosensors due to the generation of high field enhancements close to a metal or metal oxide surface, which has been shown to improve the excitation rate, quantum yield, photostability, and radiation pattern of fluorophores. This article provides an overview of existing biosensors that employ various strategies for fluorescence enhancement via nanostructures and have demonstrated the potential for use as POCT. Biosensors using nanostructures such as planar substrates, freestanding nanoparticles, and metal-dielectric-metal nanocavities are discussed with an emphasis placed on technologies that have shown promise towards POCT applications without the need for centralized laboratories.
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Abstract
Metasurfaces, artificially engineered surfaces comprised of subwavelength resonators, show promise for realizing a new generation of optical materials and devices. However, current metasurface architectures suffer from environmental degradation, a limited spectral range, and a lack of scalability. Here, we demonstrate a novel large-area embedded metasurface architecture that is environmentally robust and capable of a spectrally selective absorption of greater than 80% spanning from 330 to 2740 nm. These fully encapsulated metasurfaces leverage the capabilities of colloidal plasmonic nanoparticles with various crystallinities, materials, shapes, and sizes to access a larger spectral range and allow for control of nanoscale spatial losses and subsequent heat generation within the constituent elements of the metasurface. Through the selection of material, particle size, and shape, these metasurfaces can be designed across the ultraviolet (UV) to short-wave infrared (SWIR) region for various hot-electron, photodetection, photocatalysis, and photothermal processes.
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Actively Tunable Metasurfaces via Plasmonic Nanogap Cavities with Sub-10-nm VO 2 Films. NANO LETTERS 2022; 22:3525-3531. [PMID: 35472261 PMCID: PMC9101075 DOI: 10.1021/acs.nanolett.1c04175] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 03/20/2022] [Indexed: 05/31/2023]
Abstract
Actively tunable optical materials integrated with engineered subwavelength structures could enable novel optoelectronic devices, including reconfigurable light sources and tunable on-chip spectral filters. The phase-change material vanadium dioxide (VO2) provides a promising solid-state solution for dynamic tuning; however, previous demonstrations have been limited to thicker and often rough VO2 films or require a lattice-matched substrate for growth. Here, sub-10-nm-thick VO2 films are realized by atomic layer deposition (ALD) and integrated with plasmonic nanogap cavities to demonstrate tunable, spectrally selective absorption across 1200 nm in the near-infrared (NIR). Upon inducing the phase transition via heating, the absorption resonance is blue-shifted by as much as 60 nm. This process is reversible upon cooling and repeatable over more than ten temperature cycles. Dynamic, ultrathin VO2 films deposited by ALD, as demonstrated here, open up new potential architectures and applications where VO2 can be utilized to provide reconfigurability including three-dimensional, flexible and large-area structures.
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Ultrafast Lifetime and Bright Emission from Graphene Quantum Dots Using Plasmonic Nanogap Cavities. NANO LETTERS 2022; 22:904-910. [PMID: 35044773 DOI: 10.1021/acs.nanolett.1c03419] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Graphene quantum dots (GQDs) are quasi-zero-dimensional, carbon-based luminescent nanomaterials that possess desirable physical properties, such as high photostability, low cytotoxicity, good biocompatibility, and excellent water solubility; however, their long radiative lifetimes significantly limit their use in, e.g., light emitting devices where a fast spontaneous emission rate is essential. Despite a few reports on GQD fluorescence enhancements using metal nanostructures, studies of enhanced spontaneous emission rate remain outstanding. Here, we report fast and bright luminescence by coupling gap plasmon modes to nanoparticle emitters. Through precise control over the nanoparticle's local density of states (LDOS), we achieved a 220-fold increase in the PL intensity. The shortest radiative lifetime obtained was below 8.0 ps and limited by the instrument response, which is over 288-fold shorter than the lifetime of uncoupled GQDs. These findings may benefit the future development of rapid displays and open the possibility of constructing high-frequency classical or quantum telecommunication systems.
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Ultrasensitive point-of-care immunoassay for secreted glycoprotein detects Ebola infection earlier than PCR. Sci Transl Med 2021; 13:13/588/eabd9696. [PMID: 33827978 DOI: 10.1126/scitranslmed.abd9696] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 03/12/2021] [Indexed: 12/23/2022]
Abstract
Ebola virus (EBOV) hemorrhagic fever outbreaks have been challenging to deter due to the lack of health care infrastructure in disease-endemic countries and a corresponding inability to diagnose and contain the disease at an early stage. EBOV vaccines and therapies have improved disease outcomes, but the advent of an affordable, easily accessed, mass-produced rapid diagnostic test (RDT) that matches the performance of more resource-intensive polymerase chain reaction (PCR) assays would be invaluable in containing future outbreaks. Here, we developed and demonstrated the performance of a new ultrasensitive point-of-care immunoassay, the EBOV D4 assay, which targets the secreted glycoprotein of EBOV. The EBOV D4 assay is 1000-fold more sensitive than the U.S. Food and Drug Administration-approved RDTs and detected EBOV infection earlier than PCR in a standard nonhuman primate model. The EBOV D4 assay is suitable for low-resource settings and may facilitate earlier detection, containment, and treatment during outbreaks of the disease.
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Ultrabright Fluorescence Readout of an Inkjet-Printed Immunoassay Using Plasmonic Nanogap Cavities. NANO LETTERS 2020; 20:4330-4336. [PMID: 32375003 PMCID: PMC7737629 DOI: 10.1021/acs.nanolett.0c01051] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Fluorescence-based microarrays are promising diagnostic tools due to their high throughput, small sample volume requirements, and multiplexing capabilities. However, their low fluorescence output has limited their implementation for in vitro diagnostics applications in point-of-care (POC) settings. Here, by integration of a sandwich immunoassay microarray within a plasmonic nanogap cavity, we demonstrate strongly enhanced fluorescence which is critical for readout by inexpensive POC detectors. The immunoassay consists of inkjet-printed antibodies on a polymer brush which is grown on a gold film. Colloidally synthesized silver nanocubes are placed on top and interact with the underlying gold film creating high local electromagnetic field enhancements. By varying the thickness of the brush from 5 to 20 nm, up to a 151-fold increase in fluorescence and 14-fold improvement in the limit-of-detection is observed for the cardiac biomarker B-type natriuretic peptide (BNP) compared to the unenhanced assay, paving the way for a new generation of POC clinical diagnostics.
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11
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Ultrafast pyroelectric photodetection with on-chip spectral filters. NATURE MATERIALS 2020; 19:158-162. [PMID: 31768011 DOI: 10.1038/s41563-019-0538-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 10/18/2019] [Indexed: 05/22/2023]
Abstract
Thermal detectors, such as bolometric, pyroelectric and thermoelectric devices, are uniquely capable of sensing incident radiation for any electromagnetic frequency; however, the response times of practical devices are typically on the millisecond scale1-7. By integrating a plasmonic metasurface with an aluminium nitride pyroelectric thin film, we demonstrate spectrally selective, room-temperature pyroelectric detectors from 660-2,000 nm with an instrument-limited 1.7 ns full width at half maximum and 700 ps rise time. Heat generated from light absorption diffuses through the subwavelength absorber into the pyroelectric film producing responsivities up to 0.18 V W-1 due to the temperature-dependent spontaneous polarization of the pyroelectric films. Moreover, finite-element simulations reveal the possibility of reaching a 25 ps full width at half maximum and 6 ps rise time rivalling that of semiconductor photodiodes8. This design approach has the potential to realize large-area, inexpensive gigahertz pyroelectric detectors for wavelength-specific detection from the ultraviolet to short-wave infrared or beyond for, for example, high-speed hyperspectral imaging.
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12
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Extreme nanophotonics from ultrathin metallic gaps. NATURE MATERIALS 2019; 18:668-678. [PMID: 30936482 DOI: 10.1038/s41563-019-0290-y] [Citation(s) in RCA: 243] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 01/16/2019] [Indexed: 05/18/2023]
Abstract
Ultrathin dielectric gaps between metals can trap plasmonic optical modes with surprisingly low loss and with volumes below 1 nm3. We review the origin and subtle properties of these modes, and show how they can be well accounted for by simple models. Particularly important is the mixing between radiating antennas and confined nanogap modes, which is extremely sensitive to precise nanogeometry, right down to the single-atom level. Coupling nanogap plasmons to electronic and vibronic transitions yields a host of phenomena including single-molecule strong coupling and molecular optomechanics, opening access to atomic-scale chemistry and materials science, as well as quantum metamaterials. Ultimate low-energy devices such as robust bottom-up assembled single-atom switches are thus in prospect.
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13
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Probing the origin of highly-efficient third-harmonic generation in plasmonic nanogaps. OPTICS EXPRESS 2018; 26:20718-20725. [PMID: 30119377 DOI: 10.1364/oe.26.020718] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 07/19/2018] [Indexed: 06/08/2023]
Abstract
Plasmonic structures can precisely localize electromagnetic energy to deep subwavelength regions resulting in significant field enhancement useful for efficient on-chip nonlinear generation. However, the origin of large nonlinear enhancements observed in plasmonic nanogap structures consisting of both dielectrics and metals is not fully understood. For the first time, here we probe the third harmonic generation (THG) from a variety of dielectric materials embedded in a nanogap plasmonic cavity. From comprehensive spectral analysis of the THG signal, we conclude that the nonlinear response results primarily from the dielectric spacer layer itself as opposed to the surrounding metal. We achieved a maximum enhancement factor of more than six orders of magnitude compared to a bare gold film, which represents a nonlinear conversion efficiency of 8.78 × 10-4%. We expect this new insight into the nonlinear response in ultrathin gaps between metals to be promising for on-chip nonlinear devices such as ultrafast optical switching and entangled photon sources.
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14
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Surpassing Single Line Width Active Tuning with Photochromic Molecules Coupled to Plasmonic Nanoantennas. NANO LETTERS 2018; 18:853-858. [PMID: 29284087 DOI: 10.1021/acs.nanolett.7b04109] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Active plasmonic nanostructures with tunable resonances promise to enable smart materials with multiple functionalities, on-chip spectral-based imaging and low-power optoelectronic devices. A variety of tunable materials have been integrated with plasmonic structures, however, the tuning range in the visible regime has been limited to less than the line width of the resonance resulting in small on/off ratios. Here we demonstrate dynamic tuning of plasmon resonances up to 71 nm through multiple cycles by incorporating photochromic molecules into plasmonic nanopatch antennas. Exposure to ultraviolet (UV) light switches the molecules into a photoactive state enabling dynamic control with on/off ratios up to 9.2 dB and a tuning figure of merit up to 1.43, defined as the ratio between the spectral shift and the initial line width of the plasmonic resonance. Moreover, the physical mechanisms underlying the large spectral shifts are elucidated by studying over 40 individual nanoantennas with fundamental resonances from 550 to 720 nm revealing good agreement with finite-element simulations.
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15
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Abstract
Coherent light sources have been demonstrated based on a wide range of nanostructures, however, little effort has been devoted to probing their underlying coherence properties. Here, we report long-range spatial coherence of lattice plasmon lasers constructed from a periodic array of gold nanoparticles and a liquid gain medium at room temperature. By combining spatial and temporal interferometry, we demonstrate millimeter-scale (∼1 mm) spatial coherence and picosecond (∼2 ps) temporal coherence. The long-range spatial coherence occurs even without the presence of strong coupling with the lattice plasmon mode extending over macroscopic distances in the lasing regime. This plasmonic lasing system thus provides a platform for understanding the emergence of long-range coherence from collections of nanoscale resonators and points toward novel types of distributed lasing sources.
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Enhanced generation and anisotropic Coulomb scattering of hot electrons in an ultra-broadband plasmonic nanopatch metasurface. Nat Commun 2017; 8:986. [PMID: 29042536 PMCID: PMC5645345 DOI: 10.1038/s41467-017-01069-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 08/15/2017] [Indexed: 11/30/2022] Open
Abstract
The creation of energetic electrons through plasmon excitation of nanostructures before thermalization has been proposed for a wide number of applications in optical energy conversion and ultrafast nanophotonics. However, the use of “nonthermal” electrons is primarily limited by both a low generation efficiency and their ultrafast decay. We report experimental and theoretical results on the use of broadband plasmonic nanopatch metasurfaces comprising a gold substrate coupled to silver nanocubes that produce large concentrations of hot electrons, which we measure using transient absorption spectroscopy. We find evidence for three subpopulations of nonthermal carriers, which we propose arise from anisotropic electron–electron scattering within sp-bands near the Fermi surface. The bimetallic character of the metasurface strongly impacts the physics, with dissipation occurring primarily in the gold, whereas the quantum process of hot electron generation takes place in both components. Our calculations show that the choice of geometry and materials is crucial for producing strong ultrafast nonthermal electron components. The creation of energetic electrons through plasmon excitation has implications in optical energy conversion and ultrafast nanophotonics. Here, the authors find evidence for three subpopulations of nonthermal carriers which arise from anisotropic electron-electron scattering near the Fermi surface.
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17
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Toward Multispectral Imaging with Colloidal Metasurface Pixels. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 27966235 DOI: 10.1002/adma.201602971] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 08/28/2016] [Indexed: 05/13/2023]
Abstract
Multispectral colloidal metasurfaces are fabricated that exhibit greater than 85% absorption and ≈100 nm linewidths by patterning film-coupled nanocubes in pixels using a fusion of bottom-up and top-down fabrication techniques over wafer-scale areas. With this technique, the authors realize a multispectral pixel array consisting of six resonances between 580 and 1125 nm and reconstruct an RGB image with 9261 color combinations.
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18
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Abstract
We present a method for colloidal synthesis of silver nanocubes and the use of these in combination with a smooth gold film, to fabricate plasmonic nanoscale patch antennas. This includes a detailed procedure for the fabrication of thin films with a well-controlled thickness over macroscopic areas using layer-by-layer deposition of polyelectrolyte polymers, namely poly(allylamine) hydrochloride (PAH) and polystyrene sulfonate (PSS). These polyelectrolyte spacer layers serve as a dielectric gap in between silver nanocubes and a gold film. By controlling the size of the nanocubes or the gap thickness, the plasmon resonance can be tuned from about 500 nm to 700 nm. Next, we demonstrate how to incorporate organic sulfo-cyanine5 carboxylic acid (Cy5) dye molecules into the dielectric polymer gap region of the nanopatch antennas. Finally, we show greatly enhanced fluorescence of the Cy5 dyes by spectrally matching the plasmon resonance with the excitation energy and the Cy5 absorption peak. The method presented here enables the fabrication of plasmonic nanopatch antennas with well-controlled dimensions utilizing colloidal synthesis and a layer-by-layer dip-coating process with the potential for low cost and large-scale production. These nanopatch antennas hold great promise for practical applications, for example in sensing, ultrafast optoelectronic devices and for high-efficiency photodetectors.
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19
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Probing the origin of excitonic states in monolayer WSe2. Sci Rep 2016; 6:22414. [PMID: 26940069 PMCID: PMC4778068 DOI: 10.1038/srep22414] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 02/15/2016] [Indexed: 11/28/2022] Open
Abstract
Two-dimensional transition metal dichalcogenides (TMDCs) have spurred excitement for potential applications in optoelectronic and valleytronic devices; however, the origin of the dynamics of excitons, trions, and other localized states in these low dimensional materials is not well-understood. Here, we experimentally probed the dynamics of excitonic states in monolayer WSe2 by investigating the temperature and polarization dependent photoluminescence (PL) spectra. Four pronounced PL peaks were identified below a temperature of 60 K at near-resonant excitation and assigned to exciton, trion and localized states from excitation power dependence measurements. We find that the localized states vanish above 65 K, while exciton and trion emission peaks remain up to room temperature. This can be explained by a multi-level model developed for conventional semiconductors and applied to monolayer TMDCs for the first time here. From this model, we estimated a lower bound of the exciton binding energy of 198 meV for monolayer WSe2 and explained the vanishing of the localized states. Additionally, we observed a rapid decrease in the degree of circular polarization of the PL at increasing temperatures indicating a relatively strong electron-phonon coupling and impurity-related scattering. Our results reveal further insight into the excitonic states in monolayer WSe2 which is critical for future practical applications.
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Ultrafast Room-Temperature Single Photon Emission from Quantum Dots Coupled to Plasmonic Nanocavities. NANO LETTERS 2016; 16:270-5. [PMID: 26606001 DOI: 10.1021/acs.nanolett.5b03724] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Efficient and bright single photon sources at room temperature are critical components for quantum information systems such as quantum key distribution, quantum state teleportation, and quantum computation. However, the intrinsic radiative lifetime of quantum emitters is typically ∼10 ns, which severely limits the maximum single photon emission rate and thus entanglement rates. Here, we demonstrate the regime of ultrafast spontaneous emission (∼10 ps) from a single quantum emitter coupled to a plasmonic nanocavity at room temperature. The nanocavity integrated with a single colloidal semiconductor quantum dot produces a 540-fold decrease in the emission lifetime and a simultaneous 1900-fold increase in the total emission intensity. At the same time, the nanocavity acts as a highly efficient optical antenna directing the emission into a single lobe normal to the surface. This plasmonic platform is a versatile geometry into which a variety of other quantum emitters, such as crystal color centers, can be integrated for directional, room-temperature single photon emission rates exceeding 80 GHz.
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21
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Large-Area Metasurface Perfect Absorbers from Visible to Near-Infrared. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:8028-34. [PMID: 26549512 DOI: 10.1002/adma.201503281] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 09/12/2015] [Indexed: 05/06/2023]
Abstract
An absorptive metasurface based on film-coupled colloidal silver nanocubes is demonstrated. The metasurfaces are fabricated using simple dip-coating methods and can be deposited over large areas and on arbitrarily shaped objects. The surfaces show nearly complete absorption, good off-angle performance, and the resonance can be tuned from the visible to the near-infrared.
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22
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Leveraging Nanocavity Harmonics for Control of Optical Processes in 2D Semiconductors. NANO LETTERS 2015; 15:3578-84. [PMID: 25914964 DOI: 10.1021/acs.nanolett.5b01062] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Optical cavities with multiple tunable resonances have the potential to provide unique electromagnetic environments at two or more distinct wavelengths--critical for control of optical processes such as nonlinear generation, entangled photon generation, or photoluminescence (PL) enhancement. Here, we show a plasmonic nanocavity based on a nanopatch antenna design that has two tunable resonant modes in the visible spectrum separated by 350 nm and with line widths of ∼60 nm. The importance of utilizing two resonances simultaneously is demonstrated by integrating monolayer MoS2, a two-dimensional semiconductor, into the colloidally synthesized nanocavities. We observe a 2000-fold enhancement in the PL intensity of MoS2--which has intrinsically low absorption and small quantum yield--at room temperature, enabled by the combination of tailored absorption enhancement at the first harmonic and PL quantum-yield enhancement at the fundamental resonance.
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23
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Correction to High purcell factor due to coupling of a single emitter to a dielectric slot waveguide. NANO LETTERS 2015; 15:2763. [PMID: 25763978 DOI: 10.1021/acs.nanolett.5b00900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
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24
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High purcell factor due to coupling of a single emitter to a dielectric slot waveguide. NANO LETTERS 2015; 15:464-468. [PMID: 25432015 DOI: 10.1021/nl5037808] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate an all-dielectric quantum electrodynamical nanowire-slab system with a single emitter that concentrates the extremely intense light at the scale of 10 × 75 nm(2). The quantum dot exhibits a record high 31-fold spontaneous decay rate enhancement, its optical saturation and blinking are strongly suppressed, and 80% of emission couples into a waveguide mode.
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25
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Control of radiative processes using tunable plasmonic nanopatch antennas. NANO LETTERS 2014; 14:4797-802. [PMID: 25020029 DOI: 10.1021/nl501976f] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The radiative processes associated with fluorophores and other radiating systems can be profoundly modified by their interaction with nanoplasmonic structures. Extreme electromagnetic environments can be created in plasmonic nanostructures or nanocavities, such as within the nanoscale gap region between two plasmonic nanoparticles, where the illuminating optical fields and the density of radiating modes are dramatically enhanced relative to vacuum. Unraveling the various mechanisms present in such coupled systems, and their impact on spontaneous emission and other radiative phenomena, however, requires a suitably reliable and precise means of tuning the plasmon resonance of the nanostructure while simultaneously preserving the electromagnetic characteristics of the enhancement region. Here, we achieve this control using a plasmonic platform consisting of colloidally synthesized nanocubes electromagnetically coupled to a metallic film. Each nanocube resembles a nanoscale patch antenna (or nanopatch) whose plasmon resonance can be changed independent of its local field enhancement. By varying the size of the nanopatch, we tune the plasmonic resonance by ∼ 200 nm, encompassing the excitation, absorption, and emission spectra corresponding to Cy5 fluorophores embedded within the gap region between nanopatch and film. By sweeping the plasmon resonance but keeping the field enhancements roughly fixed, we demonstrate fluorescence enhancements exceeding a factor of 30,000 with detector-limited enhancements of the spontaneous emission rate by a factor of 74. The experiments are supported by finite-element simulations that reveal design rules for optimized fluorescence enhancement or large Purcell factors.
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Plasmonic Luneburg and Eaton lenses. NATURE NANOTECHNOLOGY 2011; 6:151-5. [PMID: 21258334 DOI: 10.1038/nnano.2010.282] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Accepted: 12/21/2010] [Indexed: 05/17/2023]
Abstract
Plasmonics takes advantage of the properties of surface plasmon polaritons, which are localized or propagating quasiparticles in which photons are coupled to the quasi-free electrons in metals. In particular, plasmonic devices can confine light in regions with dimensions that are smaller than the wavelength of the photons in free space, and this makes it possible to match the different length scales associated with photonics and electronics in a single nanoscale device. Broad applications of plasmonics that have been demonstrated to date include biological sensing, sub-diffraction-limit imaging, focusing and lithography and nano-optical circuitry. Plasmonics-based optical elements such as waveguides, lenses, beamsplitters and reflectors have been implemented by structuring metal surfaces or placing dielectric structures on metals to manipulate the two-dimensional surface plasmon waves. However, the abrupt discontinuities in the material properties or geometries of these elements lead to increased scattering of surface plasmon polaritons, which significantly reduces the efficiency of these components. Transformation optics provides an alternative approach to controlling the propagation of light by spatially varying the optical properties of a material. Here, motivated by this approach, we use grey-scale lithography to adiabatically tailor the topology of a dielectric layer adjacent to a metal surface to demonstrate a plasmonic Luneburg lens that can focus surface plasmon polaritons. We also make a plasmonic Eaton lens that can bend surface plasmon polaritons. Because the optical properties are changed gradually rather than abruptly in these lenses, losses due to scattering can be significantly reduced in comparison with previously reported plasmonic elements.
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Zero-field optical manipulation of magnetic ions in semiconductors. NATURE MATERIALS 2008; 7:203-208. [PMID: 18278049 DOI: 10.1038/nmat2123] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 01/17/2008] [Indexed: 05/25/2023]
Abstract
Controlling and monitoring individual spins is desirable for building spin-based devices, as well as implementing quantum information processing schemes. As with trapped ions in cold gases, magnetic ions trapped on a semiconductor lattice have uniform properties and relatively long spin lifetimes. Furthermore, diluted magnetic moments in semiconductors can be strongly coupled to the surrounding host, permitting optical or electrical spin manipulation. Here we describe the zero-field optical manipulation of a few hundred manganese ions in a single gallium arsenide quantum well. Optically created mobile electron spins dynamically generate an energy splitting of the ion spins and enable magnetic moment orientation solely by changing either photon helicity or energy. These polarized manganese spins precess in a transverse field, enabling measurements of the spin lifetimes. As the magnetic ion concentration is reduced and the manganese spin lifetime increases, coherent optical control and readout of single manganese spins in gallium arsenide should be possible.
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Abstract
Kerr rotation measurements on a single electron spin confined in a charge-tunable semiconductor quantum dot demonstrate a means to directly probe the spin off-resonance, thus minimally disturbing the system. Energy-resolved magneto-optical spectra reveal information about the optically oriented spin polarization and the transverse spin lifetime of the electron as a function of the charging of the dot. These results represent progress toward the manipulation and coupling of single spins and photons for quantum information processing.
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