Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics.It has a wide range of applications in our daily lives,including novel light sources,sensing,and information processing.It is...Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics.It has a wide range of applications in our daily lives,including novel light sources,sensing,and information processing.It is usually assumed that nonlinear frequency conversion requires large crystals that gradually accumulate a strong effect.However,the large size of nonlinear crystals is not compatible with the miniaturisation of modern photonic and optoelectronic systems.Therefore,shrinking the nonlinear structures down to the nanoscale,while keeping favourable conversion efficiencies,is of great importance for future photonics applications.In the last decade,researchers have studied the strategies for enhancing the nonlinear efficiencies at the nanoscale,e.g.by employing different nonlinear materials,resonant couplings and hybridization techniques.In this paper,we provide a compact review of the nanomaterials-based efforts,ranging from metal to dielectric and semiconductor nanostructures,including their relevant nanofabrication techniques.展开更多
Metal-organic frameworks(MOFs)have been extensively used for gas sorption,storage and separation owing to ultrahigh porosity,exceptional thermal stability,and wide structural diversity.However,when it comes to ultra-l...Metal-organic frameworks(MOFs)have been extensively used for gas sorption,storage and separation owing to ultrahigh porosity,exceptional thermal stability,and wide structural diversity.However,when it comes to ultra-low concentration gas detection,technical bottlenecks of MOFs appear due to the poor adsorption capacity at ppm-/ppblevel concentration and the limited sensitivity for signal transduction.Here,we present hybrid MOF-polymer physi-chemisorption mechanisms integrated with infrared(IR)nanoantennas for highly selective and ultrasensitive CO_(2) detection.To improve the adsorption capacity for trace amounts of gas molecules,MOFs are decorated with amino groups to introduce the chemisorption while maintaining the structural integrity for physisorption.Additionally,leveraging all major optimization methods,a multi-hotspot strategy is proposed to improve the sensitivity of nanoantennas by enhancing the near field and engineering the radiative and absorptive loss.As a benefit,we demonstrate the competitive advantages of our strategy against the state-of-the-art miniaturized IR CO_(2) sensors,including low detection limit,high sensitivity(0.18%/ppm),excellent reversibility(variation within 2%),and high selectivity(against C_(2)H_(5)OH,CH_(3)OH,N_(2)).This work provides valuable insights into the integration of advanced porous materials and nanophotonic devices,which can be further adopted in ultra-low concentration gas monitoring in industry and environmental applications.展开更多
Wavelength demultiplexing waveguide couplers have important applications in integrated nanophotonic devices. Two of the most important indicators of the quality of a wavelength demultiplexing coupler are coupling effi...Wavelength demultiplexing waveguide couplers have important applications in integrated nanophotonic devices. Two of the most important indicators of the quality of a wavelength demultiplexing coupler are coupling efficiency and splitting ratio. In this study, we utilize two asymmetric high-index dielectric nanoantennas directly positioned on top of a silicon-on insulator waveguide to realize a compact wavelength demultiplexing coupler in a communication band, which is based on the interference of the waveguide modes coupled by the two nanoantennas. We add a Au substrate for further increasing the coupling efficiency. This has constructive and destructive influences on the antenna＇s in-coupling efficiency owing to the Fabry-Perot（FP） resonance in the SiO2 layer. Therefore, we can realize a wavelength demultiplexing coupler with compact size and high coupling efficiency. This coupler has widespread applications in the areas of wavelength filters,on-chip signal processing, and integrated nanophotonic circuits.展开更多
Plasmonic nanoantennas provide unprecedented opportunities to concentrate light fields in subwavelength-sized volumes.By placing a nonlinear dielectric nanoparticle in such a hot spot,one can hope to take advantage of...Plasmonic nanoantennas provide unprecedented opportunities to concentrate light fields in subwavelength-sized volumes.By placing a nonlinear dielectric nanoparticle in such a hot spot,one can hope to take advantage of both the field enhancement provided by nanoantennas and the large,nonlinear optical susceptibility of dielectric nanoparticles.To test this concept,we combine gold gap nanoantennas with second-order,nonlinear zinc sulfide nanoparticles,and performsecond harmonic generation(SHG)spectroscopy on the combined hybrid dielectric/plasmonic nanoantennas as well as on the individual constituents.We find that SHG from the bare gold nanoantennas,even though it should be forbidden due tosymmetry reasons,is several orders ofmagnitude larger than that of the bare zinc sulfide nanoparticles.Even stronger second harmonic signals are generated by the hybrid dielectric/plasmonic nanoantennas.Control experiments with nanoantennas containing linear lanthanumfluoride nanoparticles reveal;however,that the increasedSHG efficiency of the hybrid dielectric/plasmonic nanoantennas does not depend on the nonlinear optical susceptibility of the dielectric nanoparticles but is an effect of the modification of the dielectric environment.The combination of a hybrid dielectric/plasmonic nanoantenna,which is only resonant for the incoming pump light field,with a second nanoantenna,which is resonant for the generated second harmonic light,allows for a further increase in the efficiency of SHG.As the second nanoantenna mediates the coupling of the second harmonic light to the far field,this double-resonant approach also provides us with control over the polarization of the generated light.展开更多
We fabricate Schottky contact photodetectors based on electrically contacted Au nanoantennas on p-Si for the plasmonic detection of sub-bandgap photons in the optical communications wavelength range. Based on a physic...We fabricate Schottky contact photodetectors based on electrically contacted Au nanoantennas on p-Si for the plasmonic detection of sub-bandgap photons in the optical communications wavelength range. Based on a physical model for the internal photoemission of hot carriers, photons coupled onto the Au nanoantennas excite resonant plasmons, which decay into energetic ＂hot＂ holes emitted over the Schottky barrier at the Au/p-Si interface, resulting in a photocurrent. In our device, the active Schottky area consists of Au/p-Si contact and is very small, whereas the probing pad for external electrical interconnection is larger but consists of Au/Ti/p-Si contact having a comparatively higher Schottky barrier, thus producing negligible photo and dark currents.We describe fabrication that involves an electron-beam lithography step overlaid with photolithography. This highly compact component is very promising for applications in high-density Si photonics.展开更多
Metal–dielectric nanostructures in the optical anapole modes are essential for light–matter interactions due to the low material loss and high near-field enhancement. Herein, a hybrid metal–dielectric nanoantenna c...Metal–dielectric nanostructures in the optical anapole modes are essential for light–matter interactions due to the low material loss and high near-field enhancement. Herein, a hybrid metal–dielectric nanoantenna composed of six wedgeshaped gold(Au) nanoblocks as well as silica(SiO2) and silicon(Si) nanodiscs is designed and analyzed by the finite element method(FEM). The nanoantenna exhibits flexibility in excitation and manipulation of the anapole mode through the strong coupling between the metal and dielectrics, consequently improving the near-field enhancement at the gap. By systematically optimizing the structural parameters, the electric field enhancement factors at wavelengths corresponding to the anapole modes(AM1 and AM2) can be increased to 518 and 1482, respectively. Moreover, the nanoantenna delivers great performance in optical sensing such as a sensitivity of 550 nm/RIU. The results provide guidance and insights into enhancing the coupling between metals and dielectrics for applications such as surface-enhanced Raman scattering and optical sensing.展开更多
Optical metasurfaces,i.e.arrays of nanoantennas with sub-wavelength size and separation,enable the manipulation of light-matter interactions in miniaturized optical components with no classical counterparts.Six decade...Optical metasurfaces,i.e.arrays of nanoantennas with sub-wavelength size and separation,enable the manipulation of light-matter interactions in miniaturized optical components with no classical counterparts.Six decades after the first ob-servation of the second harmonic generation(SHG)in bulk crystals,these devices are expected to break new ground in the field of nonlinear optics,shifting the focus from the phase matching approach achieved within long propagation dis-tances to that of near-field resonances interplay in leaky nanocavities.Here we review the recent progress in SHG with all-dielectric metasurfaces.We discuss the most used technological platforms which underpinned such advances and analyze different SHG control approaches.We finally compare their performances with other well-established technolo-gies,with the hope to delineate the current state-of-the-art and figure out a few scenarios in which these devices might soon offer unprecedented opportunities.展开更多
Using numerical calculation, we examine the effects of gap distance of a pair of nano gap silver prisms with rounded corners on the local light intensity enhancement. Two peaks due to localized surface plasmon （LSP）...Using numerical calculation, we examine the effects of gap distance of a pair of nano gap silver prisms with rounded corners on the local light intensity enhancement. Two peaks due to localized surface plasmon （LSP） excitation are observed in a wavelength range from 900nm to 300nm. The results demonstrate that peaks at a longer and a shorter wavelength corresponded to dipole-like and quadrupole-like LSP resonances, respectively. It is found that a gap distance up to 20 nm provides larger light intensity enhancement than that of a single silver nano prism with rounded corners. Furthermore, nano gap silver prisms are fabricated by direct focused ion beam processing, and we measure the scattering light spectrum of a pair of nano prisms by a confocal optical system. However, the two LSP peaks are not observed in visible range because the sizes of the nano gap and prisms are too large.展开更多
In this work electromagnetic properties of a new type of graphene nanoparticles are investigated. The particles consist of graphene circular and square rings, embedded in a dielectric environment. The electromagnetic ...In this work electromagnetic properties of a new type of graphene nanoparticles are investigated. The particles consist of graphene circular and square rings, embedded in a dielectric environment. The electromagnetic behavior in terms of resonant frequency position, magnitude and amplitude width for the absorption cross-section and the near electric field distribution are evaluated. Moreover, the influence of the geometrical parameters is also evaluated. The electromagnetic analysis is derived through proper full-wave numerical simulations. Numerical results show that the nanoparticles can be successfully used for the development of future graphene-based antennas operating in the TeraHertz Band.展开更多
Noble metal nanoantenna could effectively enhance light absorption and increase detection sensitivity. In this paper,we propose a periodic Ag diamond nanoantenna array to increase the absorption of thin-film solar cel...Noble metal nanoantenna could effectively enhance light absorption and increase detection sensitivity. In this paper,we propose a periodic Ag diamond nanoantenna array to increase the absorption of thin-film solar cells and to improve the detection sensitivity via localized surface plasmon resonance. The effect of nanoantenna arrays on the absorption enhancement is theoretically investigated using the finite difference time domain（FDTD） method with manipulating the spectral response by geometrical parameters of nanoantennas. A maximum absorption enhancement factor of 1.51 has been achieved in this study. In addition, the relation between resonant wavelength（intensity reflectivity） and refractive index is discussed in detail. When detecting the environmental index using resonant wavelengths, a maximum detection sensitivity of about 837 nm/RIU（refractive index unit） and a resolution of about 10-3RIU can be achieved. Moreover, when using the reflectivity, the sensitivity can be as high as 0.93 AU/RIU. Furthermore, we also have theoretically studied the effectiveness of nanoantennas in distinguishing chemical reagents, solution concentrations, and solution allocation ratios by detecting refractive index. From the results presented in this paper, we conclude that this work might be useful for biosensor detection and other types of detections.展开更多
We present a surface current method to model the graphene rectangular nanoantenna scattering in the terahertz band with Comsol. Compared with the equivalent thin slab method, the results obtained by the surface curren...We present a surface current method to model the graphene rectangular nanoantenna scattering in the terahertz band with Comsol. Compared with the equivalent thin slab method, the results obtained by the surface current method are more accurate and efficient. Then the electromagnetic scattering of circularly polarized terahertz waves on graphene nanoantennas is numerically analyzed by utilizing the surface current method. The depen- dences of the antenna resonant frequency with the circularly polarized wave on width and length are consistent with those for the linear polarized waves. These results are proved to be useful to design et^cient nanoantennas in terahertz wireless communications.展开更多
Beam deflectors are important optical elements which can control the propagation direction of the beam in free space.However,with the development of miniaturization of the optical systems,conventional reflector-based ...Beam deflectors are important optical elements which can control the propagation direction of the beam in free space.However,with the development of miniaturization of the optical systems,conventional reflector-based mechanical beam deflectors confront a huge challenge due to their large sizes and incompatibility to the device integration.Here we propose an all-dielectric flat metasurface beam deflector which is composed of a single layer array of TiO_2 nanoantennas resting on a fused-silica substrate.Numerical simulations are performed to demonstrate that the proposed deflectors are able to efficiently deflect the incident beam for different angles with transmission efficiency higher than 80%at visible frequencies.This ultrathin all-dielectric metasurface deflector may have great potential applications in integrated optics.展开更多
In this paper, new values of efficiency for coated and non-coated carbon nanotube dipole antennas are found at different ranges of length and constant radius to have an effective model in wireless communication techno...In this paper, new values of efficiency for coated and non-coated carbon nanotube dipole antennas are found at different ranges of length and constant radius to have an effective model in wireless communication technology, biomedical engineering, sensors and solar cells. The main issue is to get matching between the antenna and the feeding source (discreet port). To have the best value of matching impedance by optimization method through entering trials of impedance value the aim of this paper is to have the best result of efficiency in each length. A new value of efficiency is shown for coated carbon nanotube dipole antennas, it is about 59%.展开更多
Detecting and quantifying intracellular microRNAs(miRNAs)are a critical step in resolving a cancer diagnostic and resolving the ensemble of gene products that orchestrate the living state of cells.However,the nanoprob...Detecting and quantifying intracellular microRNAs(miRNAs)are a critical step in resolving a cancer diagnostic and resolving the ensemble of gene products that orchestrate the living state of cells.However,the nanoprobe for detecting low abundance miRNAs in cell cytosol is restricted by either the"one-to-one"signaltrigger model or di culty for cytosol delivery.To address these challenges,we designed a lightharvesting nanoantenna-based nanoprobe,which directs excitation energy to a single molecule to sensitively detect cytosolic miRNA.With light irradiation,the light-harvesting nanoantenna e ectively disrupted lysosomal structures by generationof reactive oxygen species,substantially achieved cytosol delivery.The nanoantenna containing>4000 donor dyes can e ciently transfer excitation energy to one or two acceptors with 99%e ciency,leading to unprecedented signal amplification and biosensing sensitivity.The designed nanoantenna can quantify cytosolic miR-210 at zeptomolar level.The fluorescence lifetime of the donor exhibited good relationship with miR-210 concentration in the range of 0.032 to 2.97 amol/ngRNA.The zeptomole sensitivity of nanoantenna provides accurate bioimaging of miR-210 both in multiple cell lines and in vivo assay,which creates a pathway for the creation of miRNA toolbox for quantitative epigenetics and personalized medicine.展开更多
Plasmonic nanoantennas provide unique opportunities for precise control of light–matter coupling in surface-enhanced infrared absorption(SEIRA)spectroscopy,but most of the resonant systems realized so far suffer from...Plasmonic nanoantennas provide unique opportunities for precise control of light–matter coupling in surface-enhanced infrared absorption(SEIRA)spectroscopy,but most of the resonant systems realized so far suffer from the obstacles of low sensitivity,narrow bandwidth,and asymmetric Fano resonance perturbations.Here,we demonstrated an overcoupled resonator with a high plasmon-molecule coupling coefficient(μ)(OC-Hμresonator)by precisely controlling the radiation loss channel,the resonator-oscillator coupling channel,and the frequency detuning channel.We observed a strong dependence of the sensing performance on the coupling state,and demonstrated that OC-Hμresonator has excellent sensing properties of ultra-sensitive(7.25%nm^(−1)),ultra-broadband(3–10μm),and immune asymmetric Fano lineshapes.These characteristics represent a breakthrough in SEIRA technology and lay the foundation for specific recognition of biomolecules,trace detection,and protein secondary structure analysis using a single array(array size is 100×100μm^(2)).In addition,with the assistance of machine learning,mixture classification,concentration prediction and spectral reconstruction were achieved with the highest accuracy of 100%.Finally,we demonstrated the potential of OC-Hμresonator for SARS-CoV-2 detection.These findings will promote the wider application of SEIRA technology,while providing new ideas for other enhanced spectroscopy technologies,quantum photonics and studying light–matter interactions.展开更多
Plasmonic nanoantennas offer new applications in mid-infrared(mid-IR)absorption spectroscopy with ultrasensitive detection of structural signatures of biomolecules,such as proteins,due to their strong resonant near-fi...Plasmonic nanoantennas offer new applications in mid-infrared(mid-IR)absorption spectroscopy with ultrasensitive detection of structural signatures of biomolecules,such as proteins,due to their strong resonant near-fields.The amide I fingerprint of a protein contains conformational information that is greatly important for understanding its function in health and disease.Here,we introduce a non-invasive,label-free mid-IR nanoantenna-array sensor for secondary structure identification of nanometer-thin protein layers in aqueous solution by resolving the content of plasmonically enhanced amide I signatures.We successfully detect random coil to crossβ-sheet conformational changes associated withα-synuclein protein aggregation,a detrimental process in many neurodegenerative disorders.Notably,our experimental results demonstrate high conformational sensitivity by differentiating subtle secondary-structural variations in a nativeβ-sheet protein monolayer from those of crossβ-sheets,which are characteristic of pathological aggregates.Our nanoplasmonic biosensor is a highly promising and versatile tool for in vitro structural analysis of thin protein layers.展开更多
The interference of optically induced electric and magnetic resonances in high-refractive-index dielectric nanoparticles provides a new approach to control and shape the scattering patterns of light in the field of na...The interference of optically induced electric and magnetic resonances in high-refractive-index dielectric nanoparticles provides a new approach to control and shape the scattering patterns of light in the field of nanophotonics. In this Letter, we spectrally tune the electric and magnetic resonances by varying the geometry of a single isolated lead telluride （PbTe） dielectric nanocube. Then, we overlap the electric dipole resonance and magnetic dipole resonance to suppress backward scattering and enhance forward scattering in the resonance region. Furthermore, a broadband unidirectional scattering is achieved by structuring the dielectric nanocuboids as a trimer antenna.展开更多
We report long-lived,highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles—nanosponges—with high excitation efficiency.It is well known that disorder on the nanometer scale,partic...We report long-lived,highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles—nanosponges—with high excitation efficiency.It is well known that disorder on the nanometer scale,particularly in two-dimensional systems,can lead to plasmon localization and large field enhancements,which can,in turn,be used to enhance nonlinear optical effects and to study and exploit quantum optical processes.Here,we introduce promising,three-dimensional model systems for light capture and plasmon localization as gold nanosponges that are formed by the dewetting of gold/silver bilayers and dealloying.We study light-induced electron emission from single nanosponges,a nonlinear process with exponents of n≈5...7,using ultrashort laser pulse excitation to achieve femtosecond time resolution.The long-lived electron emission process proves,in combination with optical extinction measurements and finite-difference time-domain calculations,the existence of localized modes with lifetimes of more than 20 fs.These electrons couple efficiently to the dipole antenna mode of each individual nanosponge,which in turn couples to the far-field.Thus,individual gold nanosponges are cheap and robust disordered nanoantennas with strong local resonances,and an ensemble of nanosponges constitutes a meta material with a strong polarization independent,nonlinear response over a wide frequency range.展开更多
Nanoscale devices in which the interaction with light can be configured using external control signals hold great interest for next-generation optoelectronic circuits.Materials exhibiting a structural or electronic ph...Nanoscale devices in which the interaction with light can be configured using external control signals hold great interest for next-generation optoelectronic circuits.Materials exhibiting a structural or electronic phase transition offer a large modulation contrast with multi-level optical switching and memory functionalities.In addition,plasmonic nanoantennas can provide an efficient enhancement mechanism for both the optically induced excitation and the readout of materials strategically positioned in their local environment.Here,we demonstrate picosecond all-optical switching of the local phase transition in plasmonic antenna-vanadium dioxide(VO_(2))hybrids,exploiting strong resonant field enhancement and selective optical pumping in plasmonic hotspots.Polarization-and wavelength-dependent pump–probe spectroscopy of multifrequency crossed antenna arrays shows that nanoscale optical switching in plasmonic hotspots does not affect neighboring antennas placed within 100 nm of the excited antennas.The antenna-assisted pumping mechanism is confirmed by numerical model calculations of the resonant,antenna-mediated local heating on a picosecond time scale.The hybrid,nanoscale excitation mechanism results in 20 times reduced switching energies and 5 times faster recovery times than a VO_(2) film without antennas,enabling fully reversible switching at over two million cycles per second and at local switching energies in the picojoule range.The hybrid solution of antennas and VO_(2) provides a conceptual framework to merge the field localization and phase-transition response,enabling precise,nanoscale optical memory functionalities.展开更多
Photonic integrated circuits are developing as key enabling components for high-performance computing and advanced networkon-chip,as well as other emerging technologies such as lab-on-chip sensors,with relevant applic...Photonic integrated circuits are developing as key enabling components for high-performance computing and advanced networkon-chip,as well as other emerging technologies such as lab-on-chip sensors,with relevant applications in areas from medicine and biotechnology to aerospace.These demanding applications will require novel features,such as dynamically reconfigurable light pathways,obtained by properly harnessing on-chip optical radiation.In this paper,we introduce a broadband,high directivity(4150),low loss and reconfigurable silicon photonics nanoantenna that fully enables on-chip radiation control.We propose the use of these nanoantennas as versatile building blocks to develop wireless(unguided)silicon photonic devices,which considerably enhance the range of achievable integrated photonic functionalities.As examples of applications,we demonstrate 160 Gbit s−1 data transmission over mm-scale wireless interconnects,a compact low-crosstalk 12-port crossing and electrically reconfigurable pathways via optical beam steering.Moreover,the realization of a flow micro-cytometer for particle characterization demonstrates the smart system integration potential of our approach as lab-on-chip devices.展开更多
文摘Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics.It has a wide range of applications in our daily lives,including novel light sources,sensing,and information processing.It is usually assumed that nonlinear frequency conversion requires large crystals that gradually accumulate a strong effect.However,the large size of nonlinear crystals is not compatible with the miniaturisation of modern photonic and optoelectronic systems.Therefore,shrinking the nonlinear structures down to the nanoscale,while keeping favourable conversion efficiencies,is of great importance for future photonics applications.In the last decade,researchers have studied the strategies for enhancing the nonlinear efficiencies at the nanoscale,e.g.by employing different nonlinear materials,resonant couplings and hybridization techniques.In this paper,we provide a compact review of the nanomaterials-based efforts,ranging from metal to dielectric and semiconductor nanostructures,including their relevant nanofabrication techniques.
基金This work is supported by the RIE Advanced Manufacturing and Engineering(AME)Programmatic Grant Project(Grant A18A5b0056,WBS:A-0005117-02-00)the Advanced Research and Technology Innovation Centre(ARTIC)Project(WBS:A-0005947-20-00)the Ministry of Education(MOE)of Singapore Tier 1 Project(WBS:A-0005138-01-00).
文摘Metal-organic frameworks(MOFs)have been extensively used for gas sorption,storage and separation owing to ultrahigh porosity,exceptional thermal stability,and wide structural diversity.However,when it comes to ultra-low concentration gas detection,technical bottlenecks of MOFs appear due to the poor adsorption capacity at ppm-/ppblevel concentration and the limited sensitivity for signal transduction.Here,we present hybrid MOF-polymer physi-chemisorption mechanisms integrated with infrared(IR)nanoantennas for highly selective and ultrasensitive CO_(2) detection.To improve the adsorption capacity for trace amounts of gas molecules,MOFs are decorated with amino groups to introduce the chemisorption while maintaining the structural integrity for physisorption.Additionally,leveraging all major optimization methods,a multi-hotspot strategy is proposed to improve the sensitivity of nanoantennas by enhancing the near field and engineering the radiative and absorptive loss.As a benefit,we demonstrate the competitive advantages of our strategy against the state-of-the-art miniaturized IR CO_(2) sensors,including low detection limit,high sensitivity(0.18%/ppm),excellent reversibility(variation within 2%),and high selectivity(against C_(2)H_(5)OH,CH_(3)OH,N_(2)).This work provides valuable insights into the integration of advanced porous materials and nanophotonic devices,which can be further adopted in ultra-low concentration gas monitoring in industry and environmental applications.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0205700 and 2015CB932403)the National Natural Science Foundation of China(Grant Nos.11174062,51472057,and 21790364)
文摘Wavelength demultiplexing waveguide couplers have important applications in integrated nanophotonic devices. Two of the most important indicators of the quality of a wavelength demultiplexing coupler are coupling efficiency and splitting ratio. In this study, we utilize two asymmetric high-index dielectric nanoantennas directly positioned on top of a silicon-on insulator waveguide to realize a compact wavelength demultiplexing coupler in a communication band, which is based on the interference of the waveguide modes coupled by the two nanoantennas. We add a Au substrate for further increasing the coupling efficiency. This has constructive and destructive influences on the antenna＇s in-coupling efficiency owing to the Fabry-Perot（FP） resonance in the SiO2 layer. Therefore, we can realize a wavelength demultiplexing coupler with compact size and high coupling efficiency. This coupler has widespread applications in the areas of wavelength filters,on-chip signal processing, and integrated nanophotonic circuits.
基金support from the Deutsche Forschungsgemeinschaft(SPP1391 and SFB TRR 142)。
文摘Plasmonic nanoantennas provide unprecedented opportunities to concentrate light fields in subwavelength-sized volumes.By placing a nonlinear dielectric nanoparticle in such a hot spot,one can hope to take advantage of both the field enhancement provided by nanoantennas and the large,nonlinear optical susceptibility of dielectric nanoparticles.To test this concept,we combine gold gap nanoantennas with second-order,nonlinear zinc sulfide nanoparticles,and performsecond harmonic generation(SHG)spectroscopy on the combined hybrid dielectric/plasmonic nanoantennas as well as on the individual constituents.We find that SHG from the bare gold nanoantennas,even though it should be forbidden due tosymmetry reasons,is several orders ofmagnitude larger than that of the bare zinc sulfide nanoparticles.Even stronger second harmonic signals are generated by the hybrid dielectric/plasmonic nanoantennas.Control experiments with nanoantennas containing linear lanthanumfluoride nanoparticles reveal;however,that the increasedSHG efficiency of the hybrid dielectric/plasmonic nanoantennas does not depend on the nonlinear optical susceptibility of the dielectric nanoparticles but is an effect of the modification of the dielectric environment.The combination of a hybrid dielectric/plasmonic nanoantenna,which is only resonant for the incoming pump light field,with a second nanoantenna,which is resonant for the generated second harmonic light,allows for a further increase in the efficiency of SHG.As the second nanoantenna mediates the coupling of the second harmonic light to the far field,this double-resonant approach also provides us with control over the polarization of the generated light.
文摘We fabricate Schottky contact photodetectors based on electrically contacted Au nanoantennas on p-Si for the plasmonic detection of sub-bandgap photons in the optical communications wavelength range. Based on a physical model for the internal photoemission of hot carriers, photons coupled onto the Au nanoantennas excite resonant plasmons, which decay into energetic ＂hot＂ holes emitted over the Schottky barrier at the Au/p-Si interface, resulting in a photocurrent. In our device, the active Schottky area consists of Au/p-Si contact and is very small, whereas the probing pad for external electrical interconnection is larger but consists of Au/Ti/p-Si contact having a comparatively higher Schottky barrier, thus producing negligible photo and dark currents.We describe fabrication that involves an electron-beam lithography step overlaid with photolithography. This highly compact component is very promising for applications in high-density Si photonics.
基金Project supported by the Outstanding young and middleaged research and innovation team of Northeast Petroleum University (Grant No. KYCXTD201801)the Natural Science Foundation Projects of Heilongjiang Province of China (Grant No. LH2021F007)+3 种基金the China Postdoctoral Science Foundation (Grant No. 2020M670881)the Study Abroad returnees merit-based Aid Foundation of Heilongjiang Province of China (Grant No. 070-719900103)the Northeastern University scientific research projects (Grant No. 2019KQ74)the City University of Hong Kong Donation Research (Grant Nos. 9220061 and DON-RMG 9229021),and the City University of Hong Kong Strategic Research (Grant No. SRG 7005505)。
文摘Metal–dielectric nanostructures in the optical anapole modes are essential for light–matter interactions due to the low material loss and high near-field enhancement. Herein, a hybrid metal–dielectric nanoantenna composed of six wedgeshaped gold(Au) nanoblocks as well as silica(SiO2) and silicon(Si) nanodiscs is designed and analyzed by the finite element method(FEM). The nanoantenna exhibits flexibility in excitation and manipulation of the anapole mode through the strong coupling between the metal and dielectrics, consequently improving the near-field enhancement at the gap. By systematically optimizing the structural parameters, the electric field enhancement factors at wavelengths corresponding to the anapole modes(AM1 and AM2) can be increased to 518 and 1482, respectively. Moreover, the nanoantenna delivers great performance in optical sensing such as a sensitivity of 550 nm/RIU. The results provide guidance and insights into enhancing the coupling between metals and dielectrics for applications such as surface-enhanced Raman scattering and optical sensing.
基金financial support by ANR through the NANOPAIR project.
文摘Optical metasurfaces,i.e.arrays of nanoantennas with sub-wavelength size and separation,enable the manipulation of light-matter interactions in miniaturized optical components with no classical counterparts.Six decades after the first ob-servation of the second harmonic generation(SHG)in bulk crystals,these devices are expected to break new ground in the field of nonlinear optics,shifting the focus from the phase matching approach achieved within long propagation dis-tances to that of near-field resonances interplay in leaky nanocavities.Here we review the recent progress in SHG with all-dielectric metasurfaces.We discuss the most used technological platforms which underpinned such advances and analyze different SHG control approaches.We finally compare their performances with other well-established technolo-gies,with the hope to delineate the current state-of-the-art and figure out a few scenarios in which these devices might soon offer unprecedented opportunities.
文摘Using numerical calculation, we examine the effects of gap distance of a pair of nano gap silver prisms with rounded corners on the local light intensity enhancement. Two peaks due to localized surface plasmon （LSP） excitation are observed in a wavelength range from 900nm to 300nm. The results demonstrate that peaks at a longer and a shorter wavelength corresponded to dipole-like and quadrupole-like LSP resonances, respectively. It is found that a gap distance up to 20 nm provides larger light intensity enhancement than that of a single silver nano prism with rounded corners. Furthermore, nano gap silver prisms are fabricated by direct focused ion beam processing, and we measure the scattering light spectrum of a pair of nano prisms by a confocal optical system. However, the two LSP peaks are not observed in visible range because the sizes of the nano gap and prisms are too large.
文摘In this work electromagnetic properties of a new type of graphene nanoparticles are investigated. The particles consist of graphene circular and square rings, embedded in a dielectric environment. The electromagnetic behavior in terms of resonant frequency position, magnitude and amplitude width for the absorption cross-section and the near electric field distribution are evaluated. Moreover, the influence of the geometrical parameters is also evaluated. The electromagnetic analysis is derived through proper full-wave numerical simulations. Numerical results show that the nanoparticles can be successfully used for the development of future graphene-based antennas operating in the TeraHertz Band.
基金Project supported by the International Scientific and Technological Cooperation Projects of Guizhou Province,China(Grant No.20117035)the Program for Innovative Research Team of Guilin University of Electronic Technology,China(Grant No.IRTGUET)
文摘Noble metal nanoantenna could effectively enhance light absorption and increase detection sensitivity. In this paper,we propose a periodic Ag diamond nanoantenna array to increase the absorption of thin-film solar cells and to improve the detection sensitivity via localized surface plasmon resonance. The effect of nanoantenna arrays on the absorption enhancement is theoretically investigated using the finite difference time domain（FDTD） method with manipulating the spectral response by geometrical parameters of nanoantennas. A maximum absorption enhancement factor of 1.51 has been achieved in this study. In addition, the relation between resonant wavelength（intensity reflectivity） and refractive index is discussed in detail. When detecting the environmental index using resonant wavelengths, a maximum detection sensitivity of about 837 nm/RIU（refractive index unit） and a resolution of about 10-3RIU can be achieved. Moreover, when using the reflectivity, the sensitivity can be as high as 0.93 AU/RIU. Furthermore, we also have theoretically studied the effectiveness of nanoantennas in distinguishing chemical reagents, solution concentrations, and solution allocation ratios by detecting refractive index. From the results presented in this paper, we conclude that this work might be useful for biosensor detection and other types of detections.
文摘We present a surface current method to model the graphene rectangular nanoantenna scattering in the terahertz band with Comsol. Compared with the equivalent thin slab method, the results obtained by the surface current method are more accurate and efficient. Then the electromagnetic scattering of circularly polarized terahertz waves on graphene nanoantennas is numerically analyzed by utilizing the surface current method. The depen- dences of the antenna resonant frequency with the circularly polarized wave on width and length are consistent with those for the linear polarized waves. These results are proved to be useful to design et^cient nanoantennas in terahertz wireless communications.
基金supported in part by the National Natural Science Foundation of China under Grant (61575092)support from the Thousand Talents Program for Young Professionals,Collaborative Innovations Center of Advanced Microstructures
文摘Beam deflectors are important optical elements which can control the propagation direction of the beam in free space.However,with the development of miniaturization of the optical systems,conventional reflector-based mechanical beam deflectors confront a huge challenge due to their large sizes and incompatibility to the device integration.Here we propose an all-dielectric flat metasurface beam deflector which is composed of a single layer array of TiO_2 nanoantennas resting on a fused-silica substrate.Numerical simulations are performed to demonstrate that the proposed deflectors are able to efficiently deflect the incident beam for different angles with transmission efficiency higher than 80%at visible frequencies.This ultrathin all-dielectric metasurface deflector may have great potential applications in integrated optics.
文摘In this paper, new values of efficiency for coated and non-coated carbon nanotube dipole antennas are found at different ranges of length and constant radius to have an effective model in wireless communication technology, biomedical engineering, sensors and solar cells. The main issue is to get matching between the antenna and the feeding source (discreet port). To have the best value of matching impedance by optimization method through entering trials of impedance value the aim of this paper is to have the best result of efficiency in each length. A new value of efficiency is shown for coated carbon nanotube dipole antennas, it is about 59%.
基金supported by start-up fund of Washington State University。
文摘Detecting and quantifying intracellular microRNAs(miRNAs)are a critical step in resolving a cancer diagnostic and resolving the ensemble of gene products that orchestrate the living state of cells.However,the nanoprobe for detecting low abundance miRNAs in cell cytosol is restricted by either the"one-to-one"signaltrigger model or di culty for cytosol delivery.To address these challenges,we designed a lightharvesting nanoantenna-based nanoprobe,which directs excitation energy to a single molecule to sensitively detect cytosolic miRNA.With light irradiation,the light-harvesting nanoantenna e ectively disrupted lysosomal structures by generationof reactive oxygen species,substantially achieved cytosol delivery.The nanoantenna containing>4000 donor dyes can e ciently transfer excitation energy to one or two acceptors with 99%e ciency,leading to unprecedented signal amplification and biosensing sensitivity.The designed nanoantenna can quantify cytosolic miR-210 at zeptomolar level.The fluorescence lifetime of the donor exhibited good relationship with miR-210 concentration in the range of 0.032 to 2.97 amol/ngRNA.The zeptomole sensitivity of nanoantenna provides accurate bioimaging of miR-210 both in multiple cell lines and in vivo assay,which creates a pathway for the creation of miRNA toolbox for quantitative epigenetics and personalized medicine.
基金supported by A*STAR under the“Nanosystems at the Edge”program(Grant No.A18A4b0055)Ministry of Education(MOE)under the research grant of R-263-000-F18-112/A-0009520-01-00+1 种基金National Research Foundation Singapore grant CRP28-2022-0038the Reimagine Re-search Scheme(RRSC)Project(Grant A-0009037-02-00&A0009037-03-00)at National University of Singapore.
文摘Plasmonic nanoantennas provide unique opportunities for precise control of light–matter coupling in surface-enhanced infrared absorption(SEIRA)spectroscopy,but most of the resonant systems realized so far suffer from the obstacles of low sensitivity,narrow bandwidth,and asymmetric Fano resonance perturbations.Here,we demonstrated an overcoupled resonator with a high plasmon-molecule coupling coefficient(μ)(OC-Hμresonator)by precisely controlling the radiation loss channel,the resonator-oscillator coupling channel,and the frequency detuning channel.We observed a strong dependence of the sensing performance on the coupling state,and demonstrated that OC-Hμresonator has excellent sensing properties of ultra-sensitive(7.25%nm^(−1)),ultra-broadband(3–10μm),and immune asymmetric Fano lineshapes.These characteristics represent a breakthrough in SEIRA technology and lay the foundation for specific recognition of biomolecules,trace detection,and protein secondary structure analysis using a single array(array size is 100×100μm^(2)).In addition,with the assistance of machine learning,mixture classification,concentration prediction and spectral reconstruction were achieved with the highest accuracy of 100%.Finally,we demonstrated the potential of OC-Hμresonator for SARS-CoV-2 detection.These findings will promote the wider application of SEIRA technology,while providing new ideas for other enhanced spectroscopy technologies,quantum photonics and studying light–matter interactions.
基金supported by the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme(Grant No.682167)European Commission Horizon 2020(grant no.FETOPEN-737071)Swiss National Foundation for Science(Grant No.152958,SNF31003A_146680,P2ELP2_162116 and P300P2_171219).
文摘Plasmonic nanoantennas offer new applications in mid-infrared(mid-IR)absorption spectroscopy with ultrasensitive detection of structural signatures of biomolecules,such as proteins,due to their strong resonant near-fields.The amide I fingerprint of a protein contains conformational information that is greatly important for understanding its function in health and disease.Here,we introduce a non-invasive,label-free mid-IR nanoantenna-array sensor for secondary structure identification of nanometer-thin protein layers in aqueous solution by resolving the content of plasmonically enhanced amide I signatures.We successfully detect random coil to crossβ-sheet conformational changes associated withα-synuclein protein aggregation,a detrimental process in many neurodegenerative disorders.Notably,our experimental results demonstrate high conformational sensitivity by differentiating subtle secondary-structural variations in a nativeβ-sheet protein monolayer from those of crossβ-sheets,which are characteristic of pathological aggregates.Our nanoplasmonic biosensor is a highly promising and versatile tool for in vitro structural analysis of thin protein layers.
基金supported by the National Key Basic Research Program of China (No. 2012CB921900)the National Natural Science Foundation of China (Nos. 61377053, 11274293, and 11374286)
文摘The interference of optically induced electric and magnetic resonances in high-refractive-index dielectric nanoparticles provides a new approach to control and shape the scattering patterns of light in the field of nanophotonics. In this Letter, we spectrally tune the electric and magnetic resonances by varying the geometry of a single isolated lead telluride （PbTe） dielectric nanocube. Then, we overlap the electric dipole resonance and magnetic dipole resonance to suppress backward scattering and enhance forward scattering in the resonance region. Furthermore, a broadband unidirectional scattering is achieved by structuring the dielectric nanocuboids as a trimer antenna.
基金support by the Deutsche Forschungsgemeinschaft(SPP1839‘Tailored Disorder’,grants LI 580/12,RU 1383/5,SCHA 632/24)the Korea Foundation for the International Cooperation of Science and Technology(Global Research Laboratory project,K20815000003)+1 种基金the German-Israeli Foundation(GIF Grant No.1256)is gratefully acknowledgeda personal grant from the Studienstiftung des Deutschen Volkes.
文摘We report long-lived,highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles—nanosponges—with high excitation efficiency.It is well known that disorder on the nanometer scale,particularly in two-dimensional systems,can lead to plasmon localization and large field enhancements,which can,in turn,be used to enhance nonlinear optical effects and to study and exploit quantum optical processes.Here,we introduce promising,three-dimensional model systems for light capture and plasmon localization as gold nanosponges that are formed by the dewetting of gold/silver bilayers and dealloying.We study light-induced electron emission from single nanosponges,a nonlinear process with exponents of n≈5...7,using ultrashort laser pulse excitation to achieve femtosecond time resolution.The long-lived electron emission process proves,in combination with optical extinction measurements and finite-difference time-domain calculations,the existence of localized modes with lifetimes of more than 20 fs.These electrons couple efficiently to the dipole antenna mode of each individual nanosponge,which in turn couples to the far-field.Thus,individual gold nanosponges are cheap and robust disordered nanoantennas with strong local resonances,and an ensemble of nanosponges constitutes a meta material with a strong polarization independent,nonlinear response over a wide frequency range.
基金financially supported by EPSRC through research grant EP/J011797/1support through an EPSRC Early Career Fellowship EP/J016918/1+2 种基金financial support from Project No.FIS2013-41184-P of the Spanish Ministry of EconomyCompetitiveness,project ETORTEK IE14-393 NANOGUNE’14 of the Department of Industry of the Government of the Basque Countrysupport from the Basque Department of Education and the UPV-EHU(Grant No.IT-756-13)。
文摘Nanoscale devices in which the interaction with light can be configured using external control signals hold great interest for next-generation optoelectronic circuits.Materials exhibiting a structural or electronic phase transition offer a large modulation contrast with multi-level optical switching and memory functionalities.In addition,plasmonic nanoantennas can provide an efficient enhancement mechanism for both the optically induced excitation and the readout of materials strategically positioned in their local environment.Here,we demonstrate picosecond all-optical switching of the local phase transition in plasmonic antenna-vanadium dioxide(VO_(2))hybrids,exploiting strong resonant field enhancement and selective optical pumping in plasmonic hotspots.Polarization-and wavelength-dependent pump–probe spectroscopy of multifrequency crossed antenna arrays shows that nanoscale optical switching in plasmonic hotspots does not affect neighboring antennas placed within 100 nm of the excited antennas.The antenna-assisted pumping mechanism is confirmed by numerical model calculations of the resonant,antenna-mediated local heating on a picosecond time scale.The hybrid,nanoscale excitation mechanism results in 20 times reduced switching energies and 5 times faster recovery times than a VO_(2) film without antennas,enabling fully reversible switching at over two million cycles per second and at local switching energies in the picojoule range.The hybrid solution of antennas and VO_(2) provides a conceptual framework to merge the field localization and phase-transition response,enabling precise,nanoscale optical memory functionalities.
文摘Photonic integrated circuits are developing as key enabling components for high-performance computing and advanced networkon-chip,as well as other emerging technologies such as lab-on-chip sensors,with relevant applications in areas from medicine and biotechnology to aerospace.These demanding applications will require novel features,such as dynamically reconfigurable light pathways,obtained by properly harnessing on-chip optical radiation.In this paper,we introduce a broadband,high directivity(4150),low loss and reconfigurable silicon photonics nanoantenna that fully enables on-chip radiation control.We propose the use of these nanoantennas as versatile building blocks to develop wireless(unguided)silicon photonic devices,which considerably enhance the range of achievable integrated photonic functionalities.As examples of applications,we demonstrate 160 Gbit s−1 data transmission over mm-scale wireless interconnects,a compact low-crosstalk 12-port crossing and electrically reconfigurable pathways via optical beam steering.Moreover,the realization of a flow micro-cytometer for particle characterization demonstrates the smart system integration potential of our approach as lab-on-chip devices.
