Hyperbolic metamaterials (HMMs) have become one of the most attractive classes of metamaterials due to their wide array of applications in combination with ease of realization. Here we will discuss our recent work on “active hyperbolic metamaterials” where demonstrate enhanced light emission and extraction from metamaterials embedded with quantum dots. We will also discuss our recent efforts on realizing tunable HMMs as well as sub-wavelength cavities.
{"title":"Active hyperbolic metamaterials (Presentation Recording)","authors":"V. Menon","doi":"10.1117/12.2188255","DOIUrl":"https://doi.org/10.1117/12.2188255","url":null,"abstract":"Hyperbolic metamaterials (HMMs) have become one of the most attractive classes of metamaterials due to their wide array of applications in combination with ease of realization. Here we will discuss our recent work on “active hyperbolic metamaterials” where demonstrate enhanced light emission and extraction from metamaterials embedded with quantum dots. We will also discuss our recent efforts on realizing tunable HMMs as well as sub-wavelength cavities.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123730973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Caldwell, L. Lindsey, V. Giannini, I. Vurgaftman, T. Reinecke, S. Maier, O. Glembocki
The field of nanophotonics is based on the ability to confine light to sub-diffractional dimensions. Up until recently, research in this field has been primarily focused on the use of plasmonic metals. However, the high optical losses inherent in such metal-based surface plasmon materials has led to an ever-expanding effort to identify, low-loss alternative materials capable of supporting sub-diffractional confinement. One highly promising alternative are polar dielectric crystals whereby sub-diffraction confinement of light can be achieved through the stimulation of surface phonon polaritons within an all-dielectric, and thus low loss material system. Both SiC and hexagonal BN are two exemplary SPhP systems, which along with a whole host of alternative materials promise to transform nanophotonics and metamaterials in the mid-IR to THz spectral range. In addition to the lower losses, these materials offer novel opportunities not available with traditional plasmonics, for instance hyperbolic optical behavior in natural materials such as hBN, enabling super-resolution imaging without the need for complex fabrication. This talk will provide an overview of the SPhP phenomenon, a discussion of what makes a ‘good’ SPhP material and recent results from SiC and the naturally hyperbolic material, hBN from our research group.
{"title":"Towards low-loss, infrared and THz nanophotonics and metamaterials: surface phonon polariton modes in polar dielectric crystals (Presentation Recording)","authors":"J. Caldwell, L. Lindsey, V. Giannini, I. Vurgaftman, T. Reinecke, S. Maier, O. Glembocki","doi":"10.1117/12.2187019","DOIUrl":"https://doi.org/10.1117/12.2187019","url":null,"abstract":"The field of nanophotonics is based on the ability to confine light to sub-diffractional dimensions. Up until recently, research in this field has been primarily focused on the use of plasmonic metals. However, the high optical losses inherent in such metal-based surface plasmon materials has led to an ever-expanding effort to identify, low-loss alternative materials capable of supporting sub-diffractional confinement. One highly promising alternative are polar dielectric crystals whereby sub-diffraction confinement of light can be achieved through the stimulation of surface phonon polaritons within an all-dielectric, and thus low loss material system. Both SiC and hexagonal BN are two exemplary SPhP systems, which along with a whole host of alternative materials promise to transform nanophotonics and metamaterials in the mid-IR to THz spectral range. In addition to the lower losses, these materials offer novel opportunities not available with traditional plasmonics, for instance hyperbolic optical behavior in natural materials such as hBN, enabling super-resolution imaging without the need for complex fabrication. This talk will provide an overview of the SPhP phenomenon, a discussion of what makes a ‘good’ SPhP material and recent results from SiC and the naturally hyperbolic material, hBN from our research group.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114078697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pseudospin is of central importance in governing many unusual transport properties of graphene and other artificial systems which have pseudospins of 1/2. These unconventional transport properties are manifested in phenomena such as Klein tunneling, and collimation of electron beams in one-dimensional external potentials. Here we show that in certain photonic crystals (PCs) exhibiting conical dispersions at the center of Brillouin zone, the eigenstates near the “Dirac-like point” can be described by an effective spin-orbit Hamiltonian with a pseudospin of 1. This effective Hamiltonian describes within a unified framework the wave propagations in both positive and negative refractive index media which correspond to the upper and lower conical bands respectively. Different from a Berry phase of π for the Dirac cone of pseudospin-1/2 systems, the Berry phase for the Dirac-like cone turns out to be zero from this pseudospin-1 Hamiltonian. In addition, we found that a change of length scale of the PC can shift the Dirac-like cone rigidly up or down in frequency with its group velocity unchanged, hence mimicking a gate voltage in graphene and allowing for a simple mechanism to control the flow of pseudospin-1 photons. As a photonic analogue of electron potential, the length-scale induced Dirac-like point shift is effectively a photonic potential within the effective pseudospin-1 Hamiltonian description. At the interface of two different potentials, the 3-component spinor gives rise to distinct boundary conditions which do not require each component of the wave function to be continuous, leading to new wave transport behaviors as shown in Klein tunneling and supercollimation. For examples, the Klein tunneling of pseudospin-1 photons is much less anisotropic with reference to the incident angle than that of pseudospin-1/2 electrons, and collimation can be more robust with pseudospin-1 than pseudospin-1/2. The special wave transport properties of pseudospin-1 photons, coupled with the discovery that the effective photonic “potential” can be varied by a simple length-scale change, may offer new ways to control photon transport. We will also explore the difference between pseudospin-1 photons and pseudospin-1/2 particles when they encounter disorder.
{"title":"Transport properties of pseudospin-1 photons (Presentation Recording)","authors":"C. Chan, A. Fang, Zhao-qing Zhang, S. Louie","doi":"10.1117/12.2188907","DOIUrl":"https://doi.org/10.1117/12.2188907","url":null,"abstract":"Pseudospin is of central importance in governing many unusual transport properties of graphene and other artificial systems which have pseudospins of 1/2. These unconventional transport properties are manifested in phenomena such as Klein tunneling, and collimation of electron beams in one-dimensional external potentials. Here we show that in certain photonic crystals (PCs) exhibiting conical dispersions at the center of Brillouin zone, the eigenstates near the “Dirac-like point” can be described by an effective spin-orbit Hamiltonian with a pseudospin of 1. This effective Hamiltonian describes within a unified framework the wave propagations in both positive and negative refractive index media which correspond to the upper and lower conical bands respectively. Different from a Berry phase of π for the Dirac cone of pseudospin-1/2 systems, the Berry phase for the Dirac-like cone turns out to be zero from this pseudospin-1 Hamiltonian. In addition, we found that a change of length scale of the PC can shift the Dirac-like cone rigidly up or down in frequency with its group velocity unchanged, hence mimicking a gate voltage in graphene and allowing for a simple mechanism to control the flow of pseudospin-1 photons. As a photonic analogue of electron potential, the length-scale induced Dirac-like point shift is effectively a photonic potential within the effective pseudospin-1 Hamiltonian description. At the interface of two different potentials, the 3-component spinor gives rise to distinct boundary conditions which do not require each component of the wave function to be continuous, leading to new wave transport behaviors as shown in Klein tunneling and supercollimation. For examples, the Klein tunneling of pseudospin-1 photons is much less anisotropic with reference to the incident angle than that of pseudospin-1/2 electrons, and collimation can be more robust with pseudospin-1 than pseudospin-1/2. The special wave transport properties of pseudospin-1 photons, coupled with the discovery that the effective photonic “potential” can be varied by a simple length-scale change, may offer new ways to control photon transport. We will also explore the difference between pseudospin-1 photons and pseudospin-1/2 particles when they encounter disorder.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127673798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Litchinitser, Jingbo Sun, M. Shalaev, T. Xu, Yun Xu, A. Pandey
We show that unique optical properties of metamaterials open unlimited prospects to “engineer” light itself. For example, we demonstrate a novel way of complex light manipulation in few-mode optical fibers using metamaterials highlighting how unique properties of metamaterials, namely the ability to manipulate both electric and magnetic field components, open new degrees of freedom in engineering complex polarization states of light. We discuss several approaches to ultra-compact structured light generation, including a nanoscale beam converter based on an ultra-compact array of nano-waveguides with a circular graded distribution of channel diameters that coverts a conventional laser beam into a vortex with configurable orbital angular momentum and a novel, miniaturized astigmatic optical element based on a single biaxial hyperbolic metamaterial that enables the conversion of Hermite-Gaussian beams into vortex beams carrying an orbital angular momentum and vice versa. Such beam converters is likely to enable a new generation of on-chip or all-fiber structured light applications. We also present our initial theoretical studies predicting that vortex-based nonlinear optical processes, such as second harmonic generation or parametric amplification that rely on phase matching, will also be strongly modified in negative index materials. These studies may find applications for multidimensional information encoding, secure communications, and quantum cryptography as both spin and orbital angular momentum could be used to encode information; dispersion engineering for spontaneous parametric down-conversion; and on-chip optoelectronic signal processing.
{"title":"Structured light-matter interactions in optical nanostructures (Presentation Recording)","authors":"N. Litchinitser, Jingbo Sun, M. Shalaev, T. Xu, Yun Xu, A. Pandey","doi":"10.1117/12.2190277","DOIUrl":"https://doi.org/10.1117/12.2190277","url":null,"abstract":"We show that unique optical properties of metamaterials open unlimited prospects to “engineer” light itself. For example, we demonstrate a novel way of complex light manipulation in few-mode optical fibers using metamaterials highlighting how unique properties of metamaterials, namely the ability to manipulate both electric and magnetic field components, open new degrees of freedom in engineering complex polarization states of light. We discuss several approaches to ultra-compact structured light generation, including a nanoscale beam converter based on an ultra-compact array of nano-waveguides with a circular graded distribution of channel diameters that coverts a conventional laser beam into a vortex with configurable orbital angular momentum and a novel, miniaturized astigmatic optical element based on a single biaxial hyperbolic metamaterial that enables the conversion of Hermite-Gaussian beams into vortex beams carrying an orbital angular momentum and vice versa. Such beam converters is likely to enable a new generation of on-chip or all-fiber structured light applications. We also present our initial theoretical studies predicting that vortex-based nonlinear optical processes, such as second harmonic generation or parametric amplification that rely on phase matching, will also be strongly modified in negative index materials. These studies may find applications for multidimensional information encoding, secure communications, and quantum cryptography as both spin and orbital angular momentum could be used to encode information; dispersion engineering for spontaneous parametric down-conversion; and on-chip optoelectronic signal processing.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132844367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Capasso, D. Wintz, P. Genevet, A. Ambrosio, Alexander Woolf
In this paper, we present new results on the controlled directional steering and focusing of surface plasmon polaritons (SPPs) via 1D and 2 D metagratings by changing the angle of incidence, the incident wavelength and polarization. These findings build on previous work of our group on polarization controlled steering of SPPS using fishbone meta gratings and greatly expand on the functionality of the latter using novel designs. First we show that by creating a running wave of polarization along a one dimensional metallic metagrating consisting of subwavelength spaced rotated apertures that propagates faster than the SPP phase velocity, we can generate surface plasmon wakes, which are the two-dimensional analogue of Cherenkov radiation. The running wave of polarization travels with a speed determined by the angle of incidence and the photon spin angular momentum. We utilize this running wave of polarization to demonstrate controlled steering of the wakes by changing both the angle of incidence and the polarization of light, which we measure through near-field scanning optical microscopy. Next we report a simple 2D metagrating design strategy that can be used for focusing, polarization beam splitting, waveguide coupling, and even phase control at the focus of an SPP beam. We experimentally verify our 2D metasurface by creating a four wavelength plasmonic demultiplexer, which also has polarization selectivity (on/off). The wavelength demultiplexer is designed such that each of the four wavelengths is focused to a different spot outside of the structure. Coupling of free space light to SPPs is achieved by milling subwavelength apertures into a thin gold film. This methodology can be easily extended to any wavelength where SPPs exist, for an arbitrary number of wavelengths, and with polarization selectivity and phase control at the focus as well.
{"title":"Metagratings for tunable unidirectional steering and focusing of surface plasmons (Presentation Recording)","authors":"F. Capasso, D. Wintz, P. Genevet, A. Ambrosio, Alexander Woolf","doi":"10.1117/12.2190368","DOIUrl":"https://doi.org/10.1117/12.2190368","url":null,"abstract":"In this paper, we present new results on the controlled directional steering and focusing of surface plasmon polaritons (SPPs) via 1D and 2 D metagratings by changing the angle of incidence, the incident wavelength and polarization. These findings build on previous work of our group on polarization controlled steering of SPPS using fishbone meta gratings and greatly expand on the functionality of the latter using novel designs. First we show that by creating a running wave of polarization along a one dimensional metallic metagrating consisting of subwavelength spaced rotated apertures that propagates faster than the SPP phase velocity, we can generate surface plasmon wakes, which are the two-dimensional analogue of Cherenkov radiation. The running wave of polarization travels with a speed determined by the angle of incidence and the photon spin angular momentum. We utilize this running wave of polarization to demonstrate controlled steering of the wakes by changing both the angle of incidence and the polarization of light, which we measure through near-field scanning optical microscopy. Next we report a simple 2D metagrating design strategy that can be used for focusing, polarization beam splitting, waveguide coupling, and even phase control at the focus of an SPP beam. We experimentally verify our 2D metasurface by creating a four wavelength plasmonic demultiplexer, which also has polarization selectivity (on/off). The wavelength demultiplexer is designed such that each of the four wavelengths is focused to a different spot outside of the structure. Coupling of free space light to SPPs is achieved by milling subwavelength apertures into a thin gold film. This methodology can be easily extended to any wavelength where SPPs exist, for an arbitrary number of wavelengths, and with polarization selectivity and phase control at the focus as well.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133508280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Aghayee, Daniel E. Winkowski, P. Kanold, W. Losert
The spatial connectivity of neural circuits and the various activity patterns they exert is what forms the brain function. How these patterns link to a certain perception or a behavior is a key question in neuroscience. Recording the activity of neural circuits while manipulating arbitrary neurons leads to answering this question. That is why acquiring a fast and reliable method of stimulation and imaging a population of neurons at a single cell resolution is of great importance. Owing to the recent advancements in calcium imaging and optogenetics, tens to hundreds of neurons in a living system can be imaged and manipulated optically. We describe the adaptation of a multi-point optical method that can be used to address the specific challenges faced in the in-vivo study of neuronal networks in the cerebral cortex. One specific challenge in the cerebral cortex is that the information flows perpendicular to the surface. Therefore, addressing multiple points in a three dimensional space simultaneously is of great interest. Using a liquid crystal spatial light modulator, the wavefront of the input laser beam is modified to produce multiple focal points at different depths of the sample for true multipoint two-photon excitation.
{"title":"Multi-point optical manipulation and simultaneous imaging of neural circuits through wavefront phase modulation (Presentation Recording)","authors":"S. Aghayee, Daniel E. Winkowski, P. Kanold, W. Losert","doi":"10.1117/12.2191538","DOIUrl":"https://doi.org/10.1117/12.2191538","url":null,"abstract":"The spatial connectivity of neural circuits and the various activity patterns they exert is what forms the brain function. How these patterns link to a certain perception or a behavior is a key question in neuroscience. Recording the activity of neural circuits while manipulating arbitrary neurons leads to answering this question. That is why acquiring a fast and reliable method of stimulation and imaging a population of neurons at a single cell resolution is of great importance. Owing to the recent advancements in calcium imaging and optogenetics, tens to hundreds of neurons in a living system can be imaged and manipulated optically. We describe the adaptation of a multi-point optical method that can be used to address the specific challenges faced in the in-vivo study of neuronal networks in the cerebral cortex. One specific challenge in the cerebral cortex is that the information flows perpendicular to the surface. Therefore, addressing multiple points in a three dimensional space simultaneously is of great interest. Using a liquid crystal spatial light modulator, the wavefront of the input laser beam is modified to produce multiple focal points at different depths of the sample for true multipoint two-photon excitation.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134435052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Solid-state junctions based on a metal-insulator-semiconductor (MIS) architecture are of great interest for a number of optoelectronic applications such as photovoltaics, photoelectrochemical cells, and photodetection. One major advantage of the MIS junction compared to the closely related metal-semiconductor junction, or Schottky junction, is that the thin insulating layer (1-3 nm thick) that separates the metal and semiconductor can significantly reduce the density of undesirable interfacial mid-gap states. The reduction in mid-gap states helps “un-pin” the junction, allowing for significantly higher built-in-voltages to be achieved. A second major advantage of the MIS junction is that the thin insulating layer can also protect the underlying semiconductor from corrosion in an electrochemical environment, making the MIS architecture well-suited for application in (photo)electrochemical applications. In this presentation, discontinuous Si-based MIS junctions immersed in electrolyte are explored for use as i.) photoelectrodes for solar-water splitting in photoelectrochemical cells (PECs) and ii.) position-sensitive photodetectors. The development and optimization of MIS photoelectrodes for both of these applications relies heavily on understanding how processing of the thin SiO2 layer impacts the properties of nano- and micro-scale MIS junctions, as well as the interactions of the insulating layer with the electrolyte. In this work, we systematically explore the effects of insulator thickness, synthesis method, and chemical treatment on the photoelectrochemical and electrochemical properties of these MIS devices. It is shown that electrolyte-induced inversion plays a critical role in determining the charge carrier dynamics within the MIS photoelectrodes for both applications.
{"title":"The role of ultra-thin SiO2 layers in metal-insulator-semiconductor (MIS) photoelectrochemical devices (Presentation Recording)","authors":"D. Esposito","doi":"10.1117/12.2190513","DOIUrl":"https://doi.org/10.1117/12.2190513","url":null,"abstract":"Solid-state junctions based on a metal-insulator-semiconductor (MIS) architecture are of great interest for a number of optoelectronic applications such as photovoltaics, photoelectrochemical cells, and photodetection. One major advantage of the MIS junction compared to the closely related metal-semiconductor junction, or Schottky junction, is that the thin insulating layer (1-3 nm thick) that separates the metal and semiconductor can significantly reduce the density of undesirable interfacial mid-gap states. The reduction in mid-gap states helps “un-pin” the junction, allowing for significantly higher built-in-voltages to be achieved. A second major advantage of the MIS junction is that the thin insulating layer can also protect the underlying semiconductor from corrosion in an electrochemical environment, making the MIS architecture well-suited for application in (photo)electrochemical applications. In this presentation, discontinuous Si-based MIS junctions immersed in electrolyte are explored for use as i.) photoelectrodes for solar-water splitting in photoelectrochemical cells (PECs) and ii.) position-sensitive photodetectors. The development and optimization of MIS photoelectrodes for both of these applications relies heavily on understanding how processing of the thin SiO2 layer impacts the properties of nano- and micro-scale MIS junctions, as well as the interactions of the insulating layer with the electrolyte. In this work, we systematically explore the effects of insulator thickness, synthesis method, and chemical treatment on the photoelectrochemical and electrochemical properties of these MIS devices. It is shown that electrolyte-induced inversion plays a critical role in determining the charge carrier dynamics within the MIS photoelectrodes for both applications.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125219950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report a novel noncollinear magnetic order in individual nanostructures of a prototypical magnetic material, bilayer iron islands on Cu (111) [1]. Spin-polarized scanning tunnelling microscopy reveals a magnetic stripe phase with a period of 1.28 nm, which is identified as a one-dimensional helical spin order. Ab initio calculations reveal reduced-dimensionality-enhanced long-range antiferromagnetic interactions as the driving force of this spin order. Our findings point at the potential of nanostructured magnets to establish noncollinear magnetic order in a nanostructure, which is magnetically decoupled from the substrate. [1] S.H. Phark, J.A. Fischer, M. Corbetta, D. Sander, K. Nakamura, J. Kirschner, Nature Comm. 5, 5183 (2014).
{"title":"Helimagnetism in nanometer small bilayer iron islands (Presentation Recording)","authors":"D. Sander","doi":"10.1117/12.2191607","DOIUrl":"https://doi.org/10.1117/12.2191607","url":null,"abstract":"We report a novel noncollinear magnetic order in individual nanostructures of a prototypical magnetic material, bilayer iron islands on Cu (111) [1]. Spin-polarized scanning tunnelling microscopy reveals a magnetic stripe phase with a period of 1.28 nm, which is identified as a one-dimensional helical spin order. Ab initio calculations reveal reduced-dimensionality-enhanced long-range antiferromagnetic interactions as the driving force of this spin order. Our findings point at the potential of nanostructured magnets to establish noncollinear magnetic order in a nanostructure, which is magnetically decoupled from the substrate. [1] S.H. Phark, J.A. Fischer, M. Corbetta, D. Sander, K. Nakamura, J. Kirschner, Nature Comm. 5, 5183 (2014).","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114065748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kai Liu, N. Zhang, Dengxin Ji, Haomin Song, Xie Zeng, Qiaoqiang Gan
Potential solar energy applications of metamaterial absorbers require spectrally tunable resonance to ensure the overlap with intrinsic absorption profiles of active materials. Although those resonance peaks of metamaterial absorbers can be tuned precisely by lithography-fabricated nanopatterns with different lateral dimensions, they are too expensive for practical large-area applications. In this work, we will report another freedom to tune the spectral position of the super absorbing resonance, i.e. the spacer thickness. The structure was fabricated by evaporating an optically opaque metallic ground plate, a dielectric spacer layer, and a top metallic thin film followed by thermal annealing processes to form discrete nanoparticles. As the spacer thickness increases from 10-90 nm, two distinct shifts of the absorption peak can be observed [i.e. a blue-shift for thinner (10-30 nm) and a red-shift for thicker spacer layers (30-90 nm)]. To understand the physical mechanism, we characterized effective optical constants of top nanopattern layer and loaded them into numerical simulation models. A good agreement with experimental data was only observed in the thick spacer region (i.e. 30-90 nm). The optical behavior for thinner spacers cannot be explained by effective medium theory and interference mechanism. Therefore, a microscopic study has to be performed to reveal strongly coupled modes under metallic nanopatterns, which can be interpreted as separate antennas strongly coupled with the ground plate. Since the resonant position is sensitive to the spacer thickness, a tunable super absorbing metasurface is realizable by introducing spatial tunable materials like stretchable chemical/ biomolecules.
{"title":"Spectral tunability of the spacer layer in metasurface absorbers (Presentation Recording)","authors":"Kai Liu, N. Zhang, Dengxin Ji, Haomin Song, Xie Zeng, Qiaoqiang Gan","doi":"10.1117/12.2187672","DOIUrl":"https://doi.org/10.1117/12.2187672","url":null,"abstract":"Potential solar energy applications of metamaterial absorbers require spectrally tunable resonance to ensure the overlap with intrinsic absorption profiles of active materials. Although those resonance peaks of metamaterial absorbers can be tuned precisely by lithography-fabricated nanopatterns with different lateral dimensions, they are too expensive for practical large-area applications. In this work, we will report another freedom to tune the spectral position of the super absorbing resonance, i.e. the spacer thickness. The structure was fabricated by evaporating an optically opaque metallic ground plate, a dielectric spacer layer, and a top metallic thin film followed by thermal annealing processes to form discrete nanoparticles. As the spacer thickness increases from 10-90 nm, two distinct shifts of the absorption peak can be observed [i.e. a blue-shift for thinner (10-30 nm) and a red-shift for thicker spacer layers (30-90 nm)]. To understand the physical mechanism, we characterized effective optical constants of top nanopattern layer and loaded them into numerical simulation models. A good agreement with experimental data was only observed in the thick spacer region (i.e. 30-90 nm). The optical behavior for thinner spacers cannot be explained by effective medium theory and interference mechanism. Therefore, a microscopic study has to be performed to reveal strongly coupled modes under metallic nanopatterns, which can be interpreted as separate antennas strongly coupled with the ground plate. Since the resonant position is sensitive to the spacer thickness, a tunable super absorbing metasurface is realizable by introducing spatial tunable materials like stretchable chemical/ biomolecules.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115415372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yue Sun, S. Suchkov, A. Miroshnichenko, A. Sukhorukov
We demonstrate that a gold split-ball resonator (SBR) in the form of a spherical nanoparticle with a cut supports both optical magnetic and acoustic modes, which have strong field confinement around the cut. Such localization away from the bottom is expected to lead to an immunity to anchor loss and thus potentially high quality factors of acoustic oscillations when positioned on a substrate. As a result, when a planewave pulse excites the optical resonance, it can then efficiently drive the acoustic vibration through laser heating and/or optical forces. We estimate the overall heat variation by modelling the optical energy dissipation inside the SBR due to the dispersive and absorbing nature of gold at optical wavelengths. The optically induced force is given by the time averaged Lorentz force density. We simulate the mechanical vibrations under the optical excitation through time-dependent simulations using solid mechanics module of COMSOL software. Assuming a moderate quality factor of 10, under a plane wave pulsed laser pump which gives 100K temperature change to the SBR, both the laser heating and optical forces lead to the excitation of the acoustic mode at the same frequency with different magnitudes of 200pm and 10pm, resulting 10% and 0.5% modification of the total optical scattering, respectively. These results show that the SBRs support strong opto-mechanical coupling and are promising in applications such as surface-enhanced Raman spectroscopy and detection of localised strain.
{"title":"Opto-mechanical interactions in split ball resonators (Presentation Recording)","authors":"Yue Sun, S. Suchkov, A. Miroshnichenko, A. Sukhorukov","doi":"10.1117/12.2190289","DOIUrl":"https://doi.org/10.1117/12.2190289","url":null,"abstract":"We demonstrate that a gold split-ball resonator (SBR) in the form of a spherical nanoparticle with a cut supports both optical magnetic and acoustic modes, which have strong field confinement around the cut. Such localization away from the bottom is expected to lead to an immunity to anchor loss and thus potentially high quality factors of acoustic oscillations when positioned on a substrate. As a result, when a planewave pulse excites the optical resonance, it can then efficiently drive the acoustic vibration through laser heating and/or optical forces. We estimate the overall heat variation by modelling the optical energy dissipation inside the SBR due to the dispersive and absorbing nature of gold at optical wavelengths. The optically induced force is given by the time averaged Lorentz force density. We simulate the mechanical vibrations under the optical excitation through time-dependent simulations using solid mechanics module of COMSOL software. Assuming a moderate quality factor of 10, under a plane wave pulsed laser pump which gives 100K temperature change to the SBR, both the laser heating and optical forces lead to the excitation of the acoustic mode at the same frequency with different magnitudes of 200pm and 10pm, resulting 10% and 0.5% modification of the total optical scattering, respectively. These results show that the SBRs support strong opto-mechanical coupling and are promising in applications such as surface-enhanced Raman spectroscopy and detection of localised strain.","PeriodicalId":432358,"journal":{"name":"SPIE NanoScience + Engineering","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121610352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：