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Petronijevic E, Cesca T, Scian C, Mattei G, Li Voti R, Sibilia C, Belardini A. Extrinsic chirality tailors Stokes parameters in simple asymmetric metasurfaces. NANOSCALE 2024; 16:16477-16484. [PMID: 39163004 DOI: 10.1039/d3nr06085c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/21/2024]
Abstract
Metasurfaces tailor electromagnetic confinement at the nanoscale and can be appropriately designed for polarization-dependent light-matter interactions. Adding the asymmetry degree to the desing allows for circular polarizations of opposite handedness to be differently absorbed or emitted, which is of interest in fields spanning from chiral sensing to flat optics. Here, we show that simple, low-cost asymmetric metasurfaces can control Stokes parameters in the transmitted far-field. With only 50 nm of asymmetric plasmonic shells on self-assembled polystyrene nanospheres, our metasurfaces allow for great spectral and incident angle tunability. We first investigated broadband extrinsic chirality in metasurfaces with asymmetric plasmonic semishells; we found high extinction circular dichroism (CD) in the near-infrared range. We then excited it with linear polarization and performed hyperspectral Stokes polarimetry on the transmitted field. We showed that the S3 parameter follows the behavior of CD in extinction, and that the output field position on the Poincaré sphere can be widely controlled by using the incidence angle and wavelength. Furthermore, simulations agreed well with the experiments and showed how the near-field chiro-optical response influences the extrinsic chiral behavior in absorption and the polarization state of the transmitted field.
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Affiliation(s)
- Emilija Petronijevic
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, I-00161 Rome, Italy.
| | - Tiziana Cesca
- University of Padova, Department of Physics and Astronomy, NanoStructures Group, via Marzolo 8, I-35131 Padova, Italy
| | - Carlo Scian
- University of Padova, Department of Physics and Astronomy, NanoStructures Group, via Marzolo 8, I-35131 Padova, Italy
| | - Giovanni Mattei
- University of Padova, Department of Physics and Astronomy, NanoStructures Group, via Marzolo 8, I-35131 Padova, Italy
| | - Roberto Li Voti
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, I-00161 Rome, Italy.
| | - Concita Sibilia
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, I-00161 Rome, Italy.
| | - Alessandro Belardini
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, I-00161 Rome, Italy.
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Petronijevic E, Cesca T, Scian C, Mattei G, Voti RL, Sibilia C, Belardini A. Demonstration of extrinsic chirality in self-assembled asymmetric plasmonic metasurfaces and nanohole arrays. Sci Rep 2024; 14:17210. [PMID: 39060402 PMCID: PMC11282274 DOI: 10.1038/s41598-024-68007-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 07/17/2024] [Indexed: 07/28/2024] Open
Abstract
Chirality, the lack of mirror symmetry, can be mimicked in nanophotonics and plasmonics by breaking the symmetry in light-nanostructure interaction. Here we report on versatile use of nanosphere lithography for the fabrication of low-cost metasurfaces, which exhibit broadband handedness- and angle-dependent extinction in the near-infrared range, thus offering extrinsic chiro-optical behavior. We measure wavelength and angle dependence of the extinction for four samples. Two samples are made of polystyrene nanospheres asymmetrically covered by silver and gold in one case and silver only in the other case, with a nanohole array at the bottom. The other two samples are nanohole arrays, obtained after the nanosphere removal from the first two samples. Rich extrinsic chiral features are governed by different chiro-optical mechanisms in the three-dimensional plasmonic semi-shells and planar nanohole arrays. We also measure Stokes parameters in the same wavelength and incidence angle range and show that the transmitted fields follow the extrinsic chirality features of the extinction dissymmetry. We further study the influences of the nanostructured shapes and in-plane orientations on the intrinsic vs extrinsic chirality. The nanoholes are modelled as oval shapes in metal, showing good agreement with the experiments. We thus confirm that nanosphere lithography can provide different geometries for chiral light manipulation at the nanoscale, with the possibility to extend functionalities with optimized oval shapes and combination of constituent metals.
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Affiliation(s)
- Emilija Petronijevic
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, 00161, Rome, Italy.
| | - T Cesca
- Physics and Astronomy Department, University of Padova, Via Marzolo 8, 35131, Padova, Italy
| | - C Scian
- Physics and Astronomy Department, University of Padova, Via Marzolo 8, 35131, Padova, Italy
| | - G Mattei
- Physics and Astronomy Department, University of Padova, Via Marzolo 8, 35131, Padova, Italy
| | - R Li Voti
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, 00161, Rome, Italy
| | - C Sibilia
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, 00161, Rome, Italy
| | - A Belardini
- Department SBAI, Sapienza University of Roma, Via A. Scarpa 14, 00161, Rome, Italy
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Murphey CGE, Park JS, Kim S, Cahoon JF. Epitaxially Grown Silicon Nanowires with a Gold Molecular Adhesion Layer for Core/Shell Structures with Compact Mie and Plasmon Resonances. ACS NANO 2023; 17:21739-21748. [PMID: 37890020 DOI: 10.1021/acsnano.3c07157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/29/2023]
Abstract
Noble-metal plasmonic nanostructures have attracted much attention because they can support deep-subwavelength optical resonances, yet their performance tends to be limited by high Ohmic absorption losses. In comparison, high-index dielectric materials can support low-loss optical resonances but do not tend to yield the same subwavelength optical confinement. Here, we combine these two approaches and examine the dielectric-plasmonic resonances in dielectric/metal core/shell nanowires. Si nanowires were grown epitaxially from (111) substrates, and direct deposition of Au on these structures by physical vapor deposition yielded nonconformal Au islands. However, by introduction of a molecular adhesion layer prior to deposition, cylindrical Si/Au core/shell nanostructures with conformal metal shells were successfully fabricated. Examining these structures as optical cavities using both optical simulations and experimental extinction measurements, we found that the structures support Mie resonances with quality factors enhanced up to ∼30 times compared with pure dielectric structures and plasmon resonances with optical confinement enhanced up to ∼5 times compared with pure metallic structures. Interestingly, extinction spectra of both Mie and plasmon resonances yield Fano line shapes, whose manifestation can be attributed to the combination of high quality factor resonances, Mie-plasmon coupling, and phase delay of the background optical field. This work demonstrates a bottom-up synthetic method for the production of freestanding, cylindrically symmetric semiconductor/metal core/shell nanowires that enables the efficient trapping of light on deep-subwavelength length scales for varied applications in photonics and optoelectronics.
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Affiliation(s)
- Corban G E Murphey
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Jin-Sung Park
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Seokhyoung Kim
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - James F Cahoon
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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Lin JX, Chen YR, Sun SJ, Hu CK, Chen BJ, Hsu HS. Field-Free Magnetoplasmon-Induced Ultraviolet Circular Dichroism Switching in Premagnetized Magnetic Nanowires. ACS APPLIED MATERIALS & INTERFACES 2022; 14:11895-11902. [PMID: 35191691 DOI: 10.1021/acsami.1c23505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Broadband modulation of magnetic circular dichroism (MCD) using a relatively low magnetic field or by producing a field-free magnetoplasmonic effect in the remnant magnetic state was achieved by the integration of the noble metals (NMs) Au and Ag and the perpendicular magnetic anisotropy of Co with ZnO nanowires (NWs) used as the template. The samples containing NMs revealed MCD sign reversals and enhancements when compared with the original Co/ZnO NWs. The magnetoplasmonic effect of Au close to the visible light spectrum could induce the CD change in the visible region. Notably, the ultraviolet (UV) CD in Ag/Co/ZnO NWs is 12.5 times larger under a magnetic field (∼0.2 T) and 10 times greater in the remnant state (field-free) than those of the original Co/ZnO NWs because of the magnetoplasmonic effect of Ag in the UV spectrum. These results are attributable to the coupling of the remnant magnetic state of Co magnetization, the magnetoplasmons of the NMs, and the excitons of the ZnO NWs. The findings are potentially applicable in magneto-optical recording, biosensing, and energy contexts involving magnetoplasmonic functionalization.
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Affiliation(s)
- Jun-Xiao Lin
- Department of Applied Physics, National Pingtung University, 4-18, Minsheng Road, Pingtung 90044, Taiwan, ROC
| | - Yu-Ren Chen
- Department of Applied Physics, National Pingtung University, 4-18, Minsheng Road, Pingtung 90044, Taiwan, ROC
| | - Shih-Jye Sun
- Department of Applied Physics, National University of Kaohsiung, 700, Kaohsiung University Road, Kaohsiung 81148, Taiwan, ROC
| | - Chun-Kai Hu
- Department of Applied Physics, National Pingtung University, 4-18, Minsheng Road, Pingtung 90044, Taiwan, ROC
| | - Bo-Jun Chen
- Department of Applied Physics, National Pingtung University, 4-18, Minsheng Road, Pingtung 90044, Taiwan, ROC
| | - Hua-Shu Hsu
- Department of Applied Physics, National Pingtung University, 4-18, Minsheng Road, Pingtung 90044, Taiwan, ROC
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Petronijevic E, Belardini A, El-ansary Z, Brioual B, Prasath Ram Kumar H, Cesca T, Scian C, Mattei G, Sibilia C. Characterization of output circular polarization degree in lowcost asymmetric metasurfaces. EPJ WEB OF CONFERENCES 2022. [DOI: 10.1051/epjconf/202226609005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Addition of asymmetry in plasmonic nanostructures can lead to chiro-optical phenomena, usually monitored as different absorption of left and right polarization, i.e. circular dichroism. Moreover, interesting features arise when the nanostructure changes the polarization state of the input beam. In this work, we perform extrinsic chirality characterization in a widely tuneable near-infrared range, by monitoring both polarization of the input and of the transmitted beam. We characterize low-cost metasurfaces based on polystyrene nanospheres asymmetrically covered by Ag, by exciting them at different angle of incidence with left, right and linear polarization. We then resolve the circular polarization degree of the transmitted beam, demonstrating resonance-governed circular polarization degree in the output, showing the interplay of both intrinsic and extrinsic chirality.
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John N, Mariamma AT. Recent developments in the chiroptical properties of chiral plasmonic gold nanostructures: bioanalytical applications. Mikrochim Acta 2021; 188:424. [PMID: 34811580 PMCID: PMC8608422 DOI: 10.1007/s00604-021-05066-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 10/14/2021] [Indexed: 11/25/2022]
Abstract
The presence of excess L-amino acid in the Murchison meteorite, circular polarization effect in the genesis of stars and existence of chirality in interstellar molecules contribute to the origin of life on earth. Chiral-sensitive techniques have been employed to untangle the secret of the symmetries of the universe, designing of effective secure drugs and investigation of chiral biomolecules. The relationship between light and chiral molecules was employed to probe and explore such molecules using spectroscopy techniques. The mutual interaction between electromagnetic spectrum and chirality of matter give rise to distinct optical response, which advances vital information contents in chiroptical spectroscopy. Chiral plasmonic gold nanoparticle exhibits distinctive circular dichroism peaks in broad wavelength range thereby crossing the limits of its characterization. The emergence of strong optical activity of gold nanosystem is related to its high polarizability, resulting in plasmonic and excitonic effects on incident photons. Inspired by the development of advanced chiral plasmonic nanomaterials and exploring its properties, this review gives an overview of various chiral gold nanostructures and the mechanism behind its chiroptical properties. Finally, we highlight the application of different chiral gold nanomaterials in the field of catalysis and medical applications with special emphasis to biosensing and biodetection.
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Affiliation(s)
- Nebu John
- The Post Graduate and Research Department of Chemistry, Mar Thoma College, Mahatma Gandhi University, Tiruvalla, 689103 Kerala India
| | - Anslin Thankachan Mariamma
- The Post Graduate Department of Mathematics, St. Gregorios College, University of Kerala, Kottarakara, 691531 Kerala India
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Aman G, Mohammadi F, Fränzl M, Lysevych M, Tan HH, Jagadish C, Schmitzer H, Cahay M, Wagner HP. Effect of Au substrate and coating on the lasing characteristics of GaAs nanowires. Sci Rep 2021; 11:21378. [PMID: 34725406 PMCID: PMC8560920 DOI: 10.1038/s41598-021-00855-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 10/18/2021] [Indexed: 11/09/2022] Open
Abstract
Optically pumped lasing from highly Zn-doped GaAs nanowires lying on an Au film substrate and from Au-coated nanowires has been demonstrated up to room temperature. The conically shaped GaAs nanowires were first coated with a 5 nm thick Al2O3 shell to suppress atmospheric oxidation and band-bending effects. Doping with a high Zn concentration increases both the radiative efficiency and the material gain and leads to lasing up to room temperature. A detailed analysis of the observed lasing behavior, using finite-difference time domain simulations, reveals that the lasing occurs from low loss hybrid modes with predominately photonic character combined with electric field enhancement effects. Achieving low loss lasing from NWs on an Au film and from Au coated nanowires opens new prospects for on-chip integration of nanolasers with new functionalities including electro-optical modulation, conductive shielding, and polarization control.
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Affiliation(s)
- Gyanan Aman
- grid.24827.3b0000 0001 2179 9593Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, OH 45221 USA
| | - Fatemesadat Mohammadi
- grid.24827.3b0000 0001 2179 9593Department of Physics, University of Cincinnati, Cincinnati, OH 45221 USA
| | - Martin Fränzl
- grid.9647.c0000 0004 7669 9786Department of Physics, University of Leipzig, 04109 Leipzig, Germany
| | - Mykhaylo Lysevych
- grid.1001.00000 0001 2180 7477Department of Electronic Materials Engineering, ARC Center of Excellence for Transformative Meta-Optical Systems, Research School of Physics, The Australian National University, Canberra, ACT 2601 Australia
| | - Hark Hoe Tan
- grid.1001.00000 0001 2180 7477Department of Electronic Materials Engineering, ARC Center of Excellence for Transformative Meta-Optical Systems, Research School of Physics, The Australian National University, Canberra, ACT 2601 Australia
| | - Chennupati Jagadish
- grid.1001.00000 0001 2180 7477Department of Electronic Materials Engineering, ARC Center of Excellence for Transformative Meta-Optical Systems, Research School of Physics, The Australian National University, Canberra, ACT 2601 Australia
| | - Heidrun Schmitzer
- grid.268352.80000 0004 1936 7849Department of Physics, Xavier University, Cincinnati, OH 45207 USA
| | - Marc Cahay
- grid.24827.3b0000 0001 2179 9593Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, OH 45221 USA
| | - Hans Peter Wagner
- grid.24827.3b0000 0001 2179 9593Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, OH 45221 USA ,grid.24827.3b0000 0001 2179 9593Department of Physics, University of Cincinnati, Cincinnati, OH 45221 USA
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Warning LA, Miandashti AR, McCarthy LA, Zhang Q, Landes CF, Link S. Nanophotonic Approaches for Chirality Sensing. ACS NANO 2021; 15:15538-15566. [PMID: 34609836 DOI: 10.1021/acsnano.1c04992] [Citation(s) in RCA: 80] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Chiral nanophotonic materials are promising candidates for biosensing applications because they focus light into nanometer dimensions, increasing their sensitivity to the molecular signatures of their surroundings. Recent advances in nanomaterial-enhanced chirality sensing provide detection limits as low as attomolar concentrations (10-18 M) for biomolecules and are relevant to the pharmaceutical industry, forensic drug testing, and medical applications that require high sensitivity. Here, we review the development of chiral nanomaterials and their application for detecting biomolecules, supramolecular structures, and other environmental stimuli. We discuss superchiral near-field generation in both dielectric and plasmonic metamaterials that are composed of chiral or achiral nanostructure arrays. These materials are also applicable for enhancing chiroptical signals from biomolecules. We review the plasmon-coupled circular dichroism mechanism observed for plasmonic nanoparticles and discuss how hotspot-enhanced plasmon-coupled circular dichroism applies to biosensing. We then review single-particle spectroscopic methods for achieving the ultimate goal of single-molecule chirality sensing. Finally, we discuss future outlooks of nanophotonic chiral systems.
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Affiliation(s)
| | | | | | - Qingfeng Zhang
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
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Plasmonic Elliptical Nanohole Arrays for Chiral Absorption and Emission in the Near-Infrared and Visible Range. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11136012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Chiral plasmonic nanostructures with tunable handedness-dependent absorption in the visible and infrared offer chiro-optical control at the nanoscale. Moreover, coupling them with emitting layers could lead to chiral nanosources, important for nanophotonic circuits. Here, we propose plasmonic elliptical nanohole arrays (ENHA) for circularly dependent near-infrared and visible emission. We first investigate broadband chiral behavior in an Au-ENHA embedded in glass by exciting it with plane waves. We then study the coupling of ENHA with a thin emitting layer embedded in glass; we focus on the emission wavelengths which provided high chirality in plane-wave simulations. Our novel simulation set-up monitors the chirality of the far-field emission by properly averaging a large set of homogeneously distributed, randomly oriented quantum sources. The intrinsic chirality of ENHA influences the circular polarization degree of the emitting layer. Finally, we study the emission dependence on the field distribution at the excitation wavelength. We demonstrate the chiral absorption and emission properties for Au-ENHA emitting in the near-infrared range, and for Ag-ENHA which is excited in green range and emits in the Lumogen Red range. The simple geometry of ENHA can be fabricated with low-cost nanosphere lithography and be covered with emission gel. We thus believe that this design can be of great importance for tunable chiral nanosources.
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Petronijevic E, Belardini A, Leahu G, Hakkarainen T, Piton MR, Koivusalo E, Sibilia C. Broadband optical spin dependent reflection in self-assembled GaAs-based nanowires asymmetrically hybridized with Au. Sci Rep 2021; 11:4316. [PMID: 33619343 PMCID: PMC7900205 DOI: 10.1038/s41598-021-83899-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/29/2020] [Indexed: 11/09/2022] Open
Abstract
Hybridization of semiconductor nanostructures with asymmetric metallic layers offers new paths to circular polarization control and chiral properties. Here we study, both experimentally and numerically, chiral properties of GaAs-based nanowires (NWs) which have two out of six sidewalls covered by Au. Sparse ensembles of vertical, free-standing NWs were fabricated by means of lithography-free self-assembled technique on Si substrates and subsequently covered by Au using tilted evaporation. We report on optical spin-dependent specular reflection in the 680–1000 nm spectral range when the orientation of the golden layers follows the rule of extrinsic chirality. The analysis shows reflection peaks of the chiral medium whose intensity is dependent on the light handedness. We further propose a novel, time-efficient numerical method that enables a better insight into the far-field intensity and distribution of the scattered light from a sparse NW ensembles. The measurements done on three different samples in various orientations show good agreement with theoretical predictions over a broad wavelength range.
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Affiliation(s)
- Emilija Petronijevic
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy.
| | - Alessandro Belardini
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy
| | - Grigore Leahu
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy
| | - Teemu Hakkarainen
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy.,Optoelectronics Research Centre, Physics Unit, Tampere University, Korkeakoulunkatu 3, 33720, Tampere, Finland
| | - Marcelo Rizzo Piton
- Optoelectronics Research Centre, Physics Unit, Tampere University, Korkeakoulunkatu 3, 33720, Tampere, Finland
| | - Eero Koivusalo
- Optoelectronics Research Centre, Physics Unit, Tampere University, Korkeakoulunkatu 3, 33720, Tampere, Finland
| | - Concita Sibilia
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy
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Circular Dichroism in the Second Harmonic Field Evidenced by Asymmetric Au Coated GaAs Nanowires. MICROMACHINES 2020; 11:mi11020225. [PMID: 32102171 PMCID: PMC7074832 DOI: 10.3390/mi11020225] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/19/2020] [Accepted: 02/20/2020] [Indexed: 12/01/2022]
Abstract
Optical circular dichroism (CD) is an important phenomenon in nanophotonics, that addresses top level applications such as circular polarized photon generation in optics, enantiomeric recognition in biophotonics and so on. Chiral nanostructures can lead to high CD, but the fabrication process usually requires a large effort, and extrinsic chiral samples can be produced by simpler techniques. Glancing angle deposition of gold on GaAs nanowires can (NWs) induces a symmetry breaking that leads to an optical CD response that mimics chiral behavior. The GaAs NWs have been fabricated by a self-catalyzed, bottom-up approach, leading to large surfaces and high-quality samples at a relatively low cost. Here, we investigate the second harmonic generation circular dichroism (SHG-CD) signal on GaAs nanowires partially covered with Au. SHG is a nonlinear process of even order, and thus extremely sensitive to symmetry breaking. Therefore, the visibility of the signal is very high when the fabricated samples present resonances at first and second harmonic frequencies (i.e., 800 and 400 nm, in our case).
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Circular Dichroism in Low-Cost Plasmonics: 2D Arrays of Nanoholes in Silver. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10041316] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Arrays of nanoholes in metal are important plasmonic devices, proposed for applications spanning from biosensing to communications. In this work, we show that in such arrays the symmetry can be broken by means of the elliptical shape of the nanoholes, combined with the in-plane tilt of the ellipse axes away from the array symmetry lines. The array then differently interacts with circular polarizations of opposite handedness at normal incidence, i.e., it becomes intrinsically chiral. The measure of this difference is called circular dichroism (CD). The nanosphere lithography combined with tilted silver evaporation was employed as a low-cost fabrication technique. In this paper, we demonstrate intrinsic chirality and CD by measuring the extinction in the near-infrared range. We further employ numerical analysis to visualize the circular polarization coupling with the nanostructure. We find a good agreement between simulations and the experiment, meaning that the optimization can be used to further increase CD.
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