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Kotte TPS, Adam AJL, Zuidwijk T, Heerkens CTH, Xu M, Urbach HP. Broadband directional scattering through a phase difference acquired in composite nanoparticles. Opt Express 2023; 31:38815-38830. [PMID: 38017976 DOI: 10.1364/oe.498461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 08/23/2023] [Indexed: 11/30/2023]
Abstract
We study the broadband scattering of light by composite nanoparticles through the Born approximation, FEM simulations, and measurements. The particles consist of two materials and show broadband directional scattering. From the analytical approach and the subsequent FEM simulations, it was found that the directional scattering is due to the phase difference between the fields scattered by of each of the two materials of the nanoparticle. To confirm this experimentally, composite nanoparticles were produced using ion-beam etching. Measurements of SiO2 / Au composite nanoparticles confirmed the directional scattering which was predicted by theory and simulations.
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Tang Y, Xi Z, Xu M, Bäumer S, Adam AJL, Urbach HP. Spatial mode-selective waveguide with hyperbolic cladding. Opt Lett 2016; 41:4285-4288. [PMID: 27628378 DOI: 10.1364/ol.41.004285] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Hyperbolic metamaterials (HMMs) are anisotropic materials with a permittivity tensor that has both positive and negative eigenvalues. Here we report that by using a type II HMM as a cladding material, a waveguide that only supports higher-order modes can be achieved, while the lower-order modes become leaky and are absorbed in the HMM cladding. This counter-intuitive property can lead to novel application in optical communications and photonic integrated circuits. The loss in our HMM insulator-HMM (HIH) waveguide is smaller than that of similar guided modes in a metal-insulator-metal (MIM) waveguide.
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Xi Z, Wei L, Adam AJL, Urbach HP, Du L. Accurate Feeding of Nanoantenna by Singular Optics for Nanoscale Translational and Rotational Displacement Sensing. Phys Rev Lett 2016; 117:113903. [PMID: 27661688 DOI: 10.1103/physrevlett.117.113903] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 06/06/2023]
Abstract
Identifying subwavelength objects and displacements is of crucial importance in optical nanometrology. We show in this Letter that nanoantennas with subwavelength structures can be excited precisely by incident beams with singularity. This accurate feeding beyond the diffraction limit can lead to dynamic control of the unidirectional scattering in the far field. The combination of the field discontinuity of the incoming singular beam with the rapid phase variation near the antenna leads to remarkable sensitivity of the far-field scattering to the displacement at a scale much smaller than the wavelength. This Letter introduces a far-field deep subwavelength position detection method based on the interaction of singular optics with nanoantennas.
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Affiliation(s)
- Zheng Xi
- Optics Research Group, Delft University of Technology, Department of Imaging Physics, Lorentzweg 1, 2628CJ Delft, The Netherlands
| | - Lei Wei
- Optics Research Group, Delft University of Technology, Department of Imaging Physics, Lorentzweg 1, 2628CJ Delft, The Netherlands
| | - A J L Adam
- Optics Research Group, Delft University of Technology, Department of Imaging Physics, Lorentzweg 1, 2628CJ Delft, The Netherlands
| | - H P Urbach
- Optics Research Group, Delft University of Technology, Department of Imaging Physics, Lorentzweg 1, 2628CJ Delft, The Netherlands
| | - Luping Du
- Nanophotonics Research Center, Shenzhen University, Nanshan District, Shenzhen, China
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Xi Z, Wei L, Adam AJL, Urbach HP. Broadband active tuning of unidirectional scattering from nanoantenna using combined radially and azimuthally polarized beams. Opt Lett 2016; 41:33-36. [PMID: 26696151 DOI: 10.1364/ol.41.000033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We propose an approach to actively tune the scattering pattern of a Mie-type spherical antenna. The scheme is based on separate control over the induced electric dipole and induced magnetic dipole using two coherent focused beams of radial polarization and azimuthal polarization, respectively. By carefully tuning the amplitude and phase relation of the two beams, a broadband unidirectional scattering can be achieved, even at the antenna's resonant wavelength where the antenna scatters efficiently. By moving the focus of one beam, a drastic switch of the unidirectional scattering can be observed. Such a scheme enables the design of ultra-compact optical switches and directional couplers based on nanoantennas.
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Knab JR, Adam AJL, Shaner E, Starmans HJAJ, Planken PCM. Terahertz near-field spectroscopy of filled subwavelength sized apertures in thin metal films. Opt Express 2013; 21:1101-1112. [PMID: 23389003 DOI: 10.1364/oe.21.001101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We have measured terahertz near-field spectra of cesium iodide crystals as small as ~10 μm in diameter, which were deposited on single, sub-wavelength-sized apertures created in thin gold films on a substrate. The advantage of using small apertures for terahertz microspectroscopy is that only terahertz light that has interacted with the cesium iodide is observed. We find that around the transverse optical phonon frequency of cesium iodide, the amplitude transmission is as much influenced by the refractive index as by the absorption. We show that the ability to measure in the near-field of the apertures, where signals are relatively strong, allows us to measure on sample volumes as small as ~5×10(-16) m(3).
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Affiliation(s)
- J R Knab
- Department of Imaging Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Delft, The Netherlands
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Vuong LT, Adam AJL, Brok JM, Planken PCM, Urbach HP. Electromagnetic spin-orbit interactions via scattering of subwavelength apertures. Phys Rev Lett 2010; 104:083903. [PMID: 20366932 DOI: 10.1103/physrevlett.104.083903] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Indexed: 05/12/2023]
Abstract
Circularly polarized electric fields incident on subwavelength apertures produce near-field phase singularities with phase vorticity +/-1 depending on the polarization handedness. These near-field phase singularities combine with those associated with orbital angular momentum and result in polarization-dependent transmission. We produce arbitrary phase vorticity in the longitudinal component of scattered electric fields by varying the incident beam and aperture configuration.
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Affiliation(s)
- L T Vuong
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York, USA.
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Guestin L, Adam AJL, Knab JR, Nagel M, Planken PCM. Influence of the dielectric substrate on the terahertz electric near-field of a hole in a metal. Opt Express 2009; 17:17412-17425. [PMID: 19907526 DOI: 10.1364/oe.17.017412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We have studied theoretically and experimentally the influence of a dielectric substrate on the frequency-dependent terahertz electric near-field of a small hole in a metal layer. We find that the near-field transmission spectrum and the two-dimensional field distribution of an empty hole in a thin metal layer on a substrate are almost identical to that of a hole which is also filled with the same dielectric material as the substrate. For thicker metal layers, however, the near-field spectra of filled and unfilled holes become very different. In addition, for thick metal layers, the two-dimensional field distributions are more strongly affected by the substrate, especially if we allow for an air gap between the metal and the substrate. Our results validate the -somewhat unusual- two-dimensional field distribution measured beneath a hole in a thick metal foil and highlight the effect that a substrate can have on the measurement of the near-field of an object.
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Affiliation(s)
- L Guestin
- Delft University of Technology, Faculty of Applied Sciences, Department of Imaging Science and Technology, Optics Research Group Lorentzweg 1, 2628 CJ Delft, The Netherlands
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Knab JR, Adam AJL, Nagel M, Shaner E, Seo MA, Kim DS, Planken PCM. Terahertz near-field vectorial imaging of subwavelength apertures and aperture arrays. Opt Express 2009; 17:15072-15086. [PMID: 19687986 DOI: 10.1364/oe.17.015072] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present measurements of the complete terahertz (THz) electric near-field distribution, E(x), E(y) and E(z), in both the time- and frequency-domains, for subwavelength apertures and subsections of subwavelength aperture arrays. Measuring the individual components of the THz near-field with subwavelength spatial resolution, as they emerge from these structures, illustrates how the field interacts with the apertures. We observe the small but measurable y- and z-components of the electric field for both single apertures and arrays. Resonant contributions, attributed to Bloch modes, are detected and we observe the presence of a longitudinal field component, E(z), within the different array apertures, which can be attributed to a diffractive effect. These measurements illustrate in detail the individual THz field components emerging from subwavelength apertures and provide a direct measure of two important mechanisms that contribute to the net transmission of light through arrays.
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Affiliation(s)
- J R Knab
- Delft University of Technology, Faculty of Applied Sciences, Department of Imaging Science and Technology, Optics Research Group, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
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Seo MA, Adam AJL, Kang JH, Lee JW, Ahn KJ, Park QH, Planken PCM, Kim DS. Near field imaging of terahertz focusing onto rectangular apertures. Opt Express 2008; 16:20484-20489. [PMID: 19065187 DOI: 10.1364/oe.16.020484] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We performed terahertz near-field experiments on single rectangular holes with various lengths grown on an electro-optic crystal substrate with lambda/100 resolution. We find that the near-field amplitude becomes proportionally larger as the rectangle becomes narrower, strongly suggesting that a constant energy passes through even for a very narrow slit. The occurrence of a large field enhancement at the fundamental localized resonance is discussed confirming the funneling of energy at the near-field.
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Affiliation(s)
- M A Seo
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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Adam AJL, Brok JM, Seo MA, Ahn KJ, Kim DS, Kang JH, Park QH, Nagel M, Planken PCM. Advanced terahertz electric near-field measurements at sub-wavelength diameter metallic apertures. Opt Express 2008; 16:7407-7417. [PMID: 18545445 DOI: 10.1364/oe.16.007407] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Using terahertz-light excitation, we have measured with sub-wavelength spatial, and sub-cycle temporal resolution the time- and frequency-dependent electric-field and surface-charge density in the vicinity of small metallic holes. In addition to a singularity like concentration of the electric field near the hole edges, we observe, that holes can act as differential operators whose near-field output is the time-derivative of the incident electric field. Our results confirm the well-known predictions made by Bouwkamp, Philips Res. Rep. 5, 321-332 (1950), and reveal, with unprecedented detail, what physically happens when light passes through a small hole.
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Affiliation(s)
- A J L Adam
- Faculty of Applied Physics, Department of Imaging Science and Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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Seo MA, Adam AJL, Kang JH, Lee JW, Jeoung SC, Park QH, Planken PCM, Kim DS. Fourier-transform terahertz near-field imaging of one-dimensional slit arrays: mapping of electric-field-, magnetic-field-, and Poynting vectors. Opt Express 2007; 15:11781-9. [PMID: 19547541 DOI: 10.1364/oe.15.011781] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We present 2D measurements of the full THz electric field behind a sample consisting of multiple slits in a metal foil. Our measurements, which have a sub-wavelength spatial, and a sub-period temporal resolution, reveal electric field lines, electric field vortices and saddle points. From our measurements we are able to reconstruct the magnetic field and, finally, the position and time-dependent Poynting vector which shows the flow of energy behind the sample. Our results show that it is possible to study the flow of light near sub-wavelength plasmonic structures such as slit-arrays and, by implication, other metamaterial samples.
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Orlova EE, Hovenier JN, Klaassen TO, Kasalynas I, Adam AJL, Gao JR, Klapwijk TM, Williams BS, Kumar S, Hu Q, Reno JL. Antenna model for wire lasers. Phys Rev Lett 2006; 96:173904. [PMID: 16712299 DOI: 10.1103/physrevlett.96.173904] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Indexed: 05/09/2023]
Abstract
An antenna model is proposed for long (L >> A) lasers with subwavelength cross sections (wire lasers). It is shown that the far-field pattern of the wire lasers is determined by the ratio of the wavelength to the length. The radiation of the wire laser is predicted to be concentrated in a narrow beam theta approximately radical(2lambda/L) for laser modes where the longitudinal phase velocity is in synchronism with the velocity of light in air. Experimental results obtained using a terahertz quantum cascade wire laser are in agreement with the model.
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Affiliation(s)
- E E Orlova
- Institute for Physics of Microstructures, Russian Academy of Sciences, Nishny Novgorod GSP-105.
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