1
|
Rohrbach D, Kang BJ, Zyaee E, Feurer T. Wideband dispersion-free THz waveguide platform. Sci Rep 2023; 13:15228. [PMID: 37709825 PMCID: PMC10502044 DOI: 10.1038/s41598-023-41843-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 08/31/2023] [Indexed: 09/16/2023] Open
Abstract
We present a versatile THz waveguide platform for frequencies between 0.1 THz and 1.5 THz, designed to exhibit vacuum-like dispersion and electric as well as magnetic field enhancement. While linear THz spectroscopy benefits from the extended interaction length in combination with moderate losses, nonlinear THz spectroscopy profits from the field enhancement and zero dispersion, with the associated reshaping-free propagation of broadband single- to few-cycle THz pulses. Moreover, the vacuum-like dispersion allows for velocity matching in mixed THz and visible to infrared pump-probe experiments. The platform is based on the motif of a metallic double ridged waveguide. We experimentally characterize essential waveguide properties, for instance, propagation and bending losses, but also demonstrate a junction and an interferometer, essentially because those elements are prerequisites for THz waveform synthesis, and hence, for coherently controlled linear and nonlinear THz interactions.
Collapse
Affiliation(s)
- David Rohrbach
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland.
| | - Bong Joo Kang
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - Elnaz Zyaee
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - Thomas Feurer
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| |
Collapse
|
2
|
Xu R, Lin T, Luo J, Chen X, Blackert ER, Moon AR, JeBailey KM, Zhu H. Phonon Polaritonics in Broad Terahertz Frequency Range with Quantum Paraelectric SrTiO 3. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2302974. [PMID: 37334883 DOI: 10.1002/adma.202302974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/08/2023] [Indexed: 06/21/2023]
Abstract
Photonics in the frequency range of 5-15 terahertz (THz) potentially open a new realm of quantum materials manipulation and biosensing. This range, sometimes called "the new terahertz gap", is traditionally difficult to access due to prevalent phonon absorption bands in solids. Low-loss phonon-polariton materials may realize sub-wavelength, on-chip photonic devices, but typically operate in mid-infrared frequencies with narrow bandwidths and are difficult to manufacture on a large scale. Here, for the first time, quantum paraelectric SrTiO3 enables broadband surface phonon-polaritonic devices in 7-13 THz. As a proof of concept, polarization-independent field concentrators are designed and fabricated to locally enhance intense, multicycle THz pulses by a factor of 6 and increase the spectral intensity by over 90 times. The time-resolved electric field inside the concentrators is experimentally measured by THz-field-induced second harmonic generation. Illuminated by a table-top light source, the average field reaches 0.5 GV m-1 over a large volume resolvable by far-field optics. These results potentially enable scalable THz photonics with high breakdown fields made of various commercially available phonon-polariton crystals for studying driven phases in quantum materials and nonlinear molecular spectroscopy.
Collapse
Affiliation(s)
- Rui Xu
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Tong Lin
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Jiaming Luo
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
- Applied Physics Graduate Program, Rice University, Houston, TX, 77005, USA
| | - Xiaotong Chen
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Elizabeth R Blackert
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Alyssa R Moon
- Nanotechnology Research Experience for Undergraduates (Nano REU) Program, Rice University, Houston, TX, 77005, USA
| | - Khalil M JeBailey
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Hanyu Zhu
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| |
Collapse
|
3
|
Haddadan F, Soroosh M, Alaei-Sheini N. Cross-talk reduction in a graphene-based ultra-compact plasmonic encoder using an Au nano-ridge on a silicon substrate. APPLIED OPTICS 2022; 61:3209-3217. [PMID: 35471301 DOI: 10.1364/ao.449123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
Plasmonic waveguides have been widely studied in the rapid development of optically integrated circuits. The cross talk between plasmonic waveguides is a critical issue that should be considered. Nano-plasmonic waveguides with tunable graphene-free patterns on silicon ridge have very attractive features. Despite these attractive features, the low confinement in plasmonic waveguides reduces the coupling length. This issue results in high cross talk in optical integrated circuits. We present a solution to the mentioned problem. A metal ridge under the plasmonic channel helps to reduce the cross-talk value. A new graphene-based plasmonic waveguide has been proposed for achieving the switching operation at terahertz frequencies. Based on the designed waveguide, a 4-to-2 plasmonic encoder with the cross talk of -17.33dB has been presented. Using six waveguides, the encoder is designed with a contrast ratio of 14.44 dB and an area of 0.36µm2. Concerning the obtained results, the presented structure can be used in optical integrated circuits.
Collapse
|
4
|
Prost E, Loriot V, Constant E, Compagnon I, Bergé L, Lépine F, Skupin S. Air-photonics terahertz platform with versatile micro-controller based interface and data acquisition. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:033004. [PMID: 35365014 DOI: 10.1063/5.0082593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/26/2022] [Indexed: 06/14/2023]
Abstract
We present a terahertz (THz) platform employing air plasma produced by an ultrashort two-color laser pulse as a broadband THz source and air biased coherent detection (ABCD) of the THz field. In contrast to previous studies, a simple peak detector connected to a micro-controller board acquires the ABCD-signal coming from the avalanche photodiode. Numerical simulations of the whole setup yield temporal and spectral profiles of the terahertz electric field in both source and detection area. The latter ones are in excellent agreement with our measurements, confirming THz electric fields with peak amplitude in the MV/cm range. We further illustrate the capabilities of the platform by performing THz spectroscopy of water vapor and a polystyrene reference sample.
Collapse
Affiliation(s)
- E Prost
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - V Loriot
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - E Constant
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - I Compagnon
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - L Bergé
- CEA, DAM, DIF, F-91297 Arpajon, France
| | - F Lépine
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - S Skupin
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| |
Collapse
|
5
|
Abstract
Terahertz time-domain spectroscopy (THz-TDS) is a non-invasive, non-contact and label-free technique for biological and chemical sensing as THz-spectra are less energetic and lie in the characteristic vibration frequency regime of proteins and DNA molecules. However, THz-TDS is less sensitive for the detection of micro-organisms of size equal to or less than λ/100 (where, λ is the wavelength of the incident THz wave), and molecules in extremely low concentration solutions (like, a few femtomolar). After successful high-throughput fabrication of nanostructures, nanoantennas were found to be indispensable in enhancing the sensitivity of conventional THz-TDS. These nanostructures lead to strong THz field enhancement when in resonance with the absorption spectrum of absorptive molecules, causing significant changes in the magnitude of the transmission spectrum, therefore, enhancing the sensitivity and allowing the detection of molecules and biomaterials in extremely low concentration solutions. Herein, we review the recent developments in ultra-sensitive and selective nanogap biosensors. We have also provided an in-depth review of various high-throughput nanofabrication techniques. We also discussed the physics behind the field enhancements in the sub-skin depth as well as sub-nanometer sized nanogaps. We introduce finite-difference time-domain (FDTD) and molecular dynamics (MD) simulation tools to study THz biomolecular interactions. Finally, we provide a comprehensive account of nanoantenna enhanced sensing of viruses (like, H1N1) and biomolecules such as artificial sweeteners which are addictive and carcinogenic.
Collapse
Affiliation(s)
- Subham Adak
- Department of Physics, Birla Institute of Technology, Mesra, Ranchi - 835215, Jharkhand, India.
| | | |
Collapse
|
6
|
Othman MAK, Hoffmann MC, Kozina ME, Wang XJ, Li RK, Nanni EA. Parallel-plate waveguides for terahertz-driven MeV electron bunch compression. OPTICS EXPRESS 2019; 27:23791-23800. [PMID: 31510279 DOI: 10.1364/oe.27.023791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 07/29/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate the electromagnetic performance of waveguides for femtosecond electron beam bunch manipulation and compression with strong-field terahertz (THz) pulses. The compressor structure is a dispersion-free exponentially-tapered parallel-plate waveguide (PPWG) that can focus single-cycle THz pulses along one dimension. We show test results of the tapered PPWG structure using electro-optic sampling (EOS) at the interaction region with peak fields of at least 300 kV/cm, given 0.9 µJ of incoming THz energy. We also present a modified shorted design of the tapered PPWG for better beam manipulation and reduced magnetic field as an alternative to a dual-feed approach. As an example, we demonstrate that with 5 µJ of THz energy, the PPWG compresses a 2.5 MeV electron bunch by a compression factor of more than 4, achieving a bunch length of about 18 fs.
Collapse
|
7
|
Abstract
This article reviews recent advances in terahertz science and technology that rely on confining the energy of incident terahertz radiation to small, very sub-wavelength sized regions. We focus on two broad areas of application for such field confinement: metamaterial-based nonlinear terahertz devices and terahertz near-field microscopy and spectroscopy techniques. In particular, we focus on field confinement in: terahertz nonlinear absorbers, metamaterial enhanced nonlinear terahertz spectroscopy, and in sub-wavelength terahertz imaging systems.
Collapse
|
8
|
Su Y, Lin Q, Zhai X, Wang LL. Enhanced Confinement of Terahertz Surface Plasmon Polaritons in Bulk Dirac Semimetal-Insulator-Metal Waveguides. NANOSCALE RESEARCH LETTERS 2018; 13:308. [PMID: 30284110 PMCID: PMC6170250 DOI: 10.1186/s11671-018-2686-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 08/24/2018] [Indexed: 06/08/2023]
Abstract
A subwavelength terahertz plasmonic waveguide based on bulk Dirac semimetal (BDS)-insulator-metal (BIM) structure is investigated, which indicates that there is an optimized frequency range with the better confinement as well as lower loss. A broadband mode confinement up to λ0/15 with a relatively low loss of 1.0 dB/λ0 can be achieved. We also show that two silicon ribbons introduced into the BIM waveguide can form a dynamically tunable filter tailoring terahertz surface plasmon polaritons in deep-subwavelength scale, which can be further exploited for the design of ultra-compact THz plasmonic devices with dynamical tunability. Our results may also provide potential applications in optical filtering.
Collapse
Affiliation(s)
- Yi Su
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, 410082 China
| | - Qi Lin
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, 410082 China
| | - Xiang Zhai
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, 410082 China
| | - Ling-Ling Wang
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, 410082 China
| |
Collapse
|
9
|
Qiu H, Kurihara T, Harada H, Kato K, Takano K, Suemoto T, Tani M, Sarukura N, Yoshimura M, Nakajima M. Enhancing terahertz magnetic near field induced by a micro-split-ring resonator with a tapered waveguide. OPTICS LETTERS 2018; 43:1658-1661. [PMID: 29652333 DOI: 10.1364/ol.43.001658] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 03/03/2018] [Indexed: 06/08/2023]
Abstract
Substantial enhancement of terahertz magnetic near field achieved by the combination of a tapered metallic waveguide and a micro-split-ring resonator is demonstrated. The magnetic near field is probed directly via the magneto-optic sampling with a Tb3Ga5O12 crystal. The incident terahertz wave with a half-cycle waveform is generated by using the pulse-front tilting method. The magnetic near field at the resonant frequency is enhanced by more than 30 times through the combination of the waveguide and the resonator. The peak amplitude of the magnetic field with a damped oscillation waveform in the time domain is up to 0.4 T. The resonant frequency can be tuned by adopting different resonator designs. The mechanism of the enhancement is analyzed by performing calculations based on the finite element method. The strong terahertz magnetic near field enables the excitation of large-amplitude spin dynamics and can be utilized for an ultrafast spin control.
Collapse
|
10
|
Ye L, Xiao Y, Liu N, Song Z, Zhang W, Liu QH. Plasmonic waveguide with folded stubs for highly confined terahertz propagation and concentration. OPTICS EXPRESS 2017; 25:898-906. [PMID: 28157978 DOI: 10.1364/oe.25.000898] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We proposed a novel planar terahertz (THz) plasmonic waveguide with folded stub arrays to achieve excellent terahertz propagation performance with tight field confinement and compact size based on the concept of spoof surface plasmon polaritons (spoof SPPs). It is found that the waveguide propagation characteristics can be directly manipulated by increasing the length of the folded stubs without increasing its lateral dimension, which exhibits much lower asymptotic frequency of the dispersion relation and even tighter terahertz field confinement than conventional plasmonic waveguides with rectangular stub arrays. Based on this waveguiding scheme, a terahertz concentrator with gradual step-length folded stubs is proposed to achieve high terahertz field enhancement, and an enhancement factor greater than 20 is demonstrated. This work offers a new perspective on very confined terahertz propagation and concentration, which may have promising potential applications in various integrated terahertz plasmonic circuits and devices, terahertz sensing and terahertz nonlinear optics.
Collapse
|
11
|
Klarskov P, Tarekegne AT, Iwaszczuk K, Zhang XC, Jepsen PU. Amplification of resonant field enhancement by plasmonic lattice coupling in metallic slit arrays. Sci Rep 2016; 6:37738. [PMID: 27886232 PMCID: PMC5123578 DOI: 10.1038/srep37738] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 11/01/2016] [Indexed: 12/03/2022] Open
Abstract
Nonlinear spectroscopic investigation in the terahertz (THz) range requires significant field strength of the light fields. It is still a challenge to obtain the required field strengths in free space from table-top laser systems at sufficiently high repetition rates to enable quantitative nonlinear spectroscopy. It is well known that local enhancement of the THz field can be obtained for instance in narrow apertures in metallic films. Here we show by simulation, analytical modelling and experiment that the achievable field enhancement in a two-dimensional array of slits with micrometer dimensions in a metallic film can be increased by at least 60% compared to the enhancement in an isolated slit. The additional enhancement is obtained by optimized plasmonic coupling between the lattice modes and the resonance of the individual slits. Our results indicate a viable route to sensitive schemes for THz spectroscopy with slit arrays manufactured by standard UV photolithography, with local field strengths in the multi-ten-MV/cm range at kHz repetition rates, and tens of kV/cm at oscillator repetition rates.
Collapse
Affiliation(s)
- Pernille Klarskov
- DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Abebe T Tarekegne
- DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Krzysztof Iwaszczuk
- DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - X-C Zhang
- Institute of Optics, University of Rochester, Rochester, NY 14627-0186, United States of America
| | - Peter Uhd Jepsen
- DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| |
Collapse
|
12
|
Savoini M, Grübel S, Bagiante S, Sigg H, Feurer T, Beaud P, Johnson SL. THz near-field enhancement by means of isolated dipolar antennas: the effect of finite sample size. OPTICS EXPRESS 2016; 24:4552-4562. [PMID: 29092282 DOI: 10.1364/oe.24.004552] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Generation of high intensity terahertz radiation in the low frequency region (f < 5 THz) is still a challenging task and only few experimental demonstrations exceeding 1 MV/cm have been reported so far. One viable option is the use of resonant metallic structures which act as amplifiers for the impinging radiation. Here with the aid of finite difference time domain simulations, we design and realize a set of isolated resonant elements which allow us to reach a 28-fold enhancement of freely propagating THz radiation at f ≈ 1 THz. These elements are deposited on a GaP sample allowing the direct measurement of the field enhancement using electro-optical sampling. Interestingly, we experimentally show strong modifications of the antennas resonance which is interpreted in terms of interference effects. These are particularly important in samples thinner than half the spatial pulse length.
Collapse
|
13
|
Zenin VA, Andryieuski A, Malureanu R, Radko IP, Volkov VS, Gramotnev DK, Lavrinenko AV, Bozhevolnyi SI. Boosting Local Field Enhancement by on-Chip Nanofocusing and Impedance-Matched Plasmonic Antennas. NANO LETTERS 2015; 15:8148-54. [PMID: 26551324 DOI: 10.1021/acs.nanolett.5b03593] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Strongly confined surface plasmon-polariton modes can be used for efficiently delivering the electromagnetic energy to nanosized volumes by reducing the cross sections of propagating modes far beyond the diffraction limit, that is, by nanofocusing. This process results in significant local-field enhancement that can advantageously be exploited in modern optical nanotechnologies, including signal processing, biochemical sensing, imaging, and spectroscopy. Here, we propose, analyze, and experimentally demonstrate on-chip nanofocusing followed by impedance-matched nanowire antenna excitation in the end-fire geometry at telecom wavelengths. Numerical and experimental evidence of the efficient excitation of dipole and quadrupole (dark) antenna modes are provided, revealing underlying physical mechanisms and analogies with the operation of plane-wave Fabry-Pérot interferometers. The unique combination of efficient nanofocusing and nanoantenna resonant excitation realized in our experiments offers a major boost to the field intensity enhancement up to ∼12000, with the enhanced field being evenly distributed over the gap volume of 30 × 30 × 10 nm(3), and promises thereby a variety of useful on-chip functionalities within sensing, nonlinear spectroscopy and signal processing.
Collapse
Affiliation(s)
- Vladimir A Zenin
- Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark
| | - Andrei Andryieuski
- DTU Fotonik, Technical University of Denmark , Oersteds pl. 343, DK-2800 Kongens Lyngby, Denmark
| | - Radu Malureanu
- DTU Fotonik, Technical University of Denmark , Oersteds pl. 343, DK-2800 Kongens Lyngby, Denmark
| | - Ilya P Radko
- Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark
| | - Valentyn S Volkov
- Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark
| | - Dmitri K Gramotnev
- Nanophotonics Pty. Ltd. , GPO Box 786, Albany Creek, Queensland 4035, Australia
| | - Andrei V Lavrinenko
- DTU Fotonik, Technical University of Denmark , Oersteds pl. 343, DK-2800 Kongens Lyngby, Denmark
| | - Sergey I Bozhevolnyi
- Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark
| |
Collapse
|
14
|
Abstract
Femtosecond electron bunches with keV energies and eV energy spread are needed by condensed matter physicists to resolve state transitions in carbon nanotubes, molecular structures, organic salts, and charge density wave materials. These semirelativistic electron sources are not only of interest for ultrafast electron diffraction, but also for electron energy-loss spectroscopy and as a seed for x-ray FELs. Thus far, the output energy spread (hence pulse duration) of ultrafast electron guns has been limited by the achievable electric field at the surface of the emitter, which is 10 MV/m for DC guns and 200 MV/m for RF guns. A single-cycle THz electron gun provides a unique opportunity to not only achieve GV/m surface electric fields but also with relatively low THz pulse energies, since a single-cycle transform-limited waveform is the most efficient way to achieve intense electric fields. Here, electron bunches of 50 fC from a flat copper photocathode are accelerated from rest to tens of eV by a microjoule THz pulse with peak electric field of 72 MV/m at 1 kHz repetition rate. We show that scaling to the readily-available GV/m THz field regime would translate to monoenergetic electron beams of ~100 keV.
Collapse
|
15
|
Kurihara K, Otomo A, Yamamoto K, Takahara J, Tani M, Kuwashima F. Identification of Plasmonic Modes in Parabolic Cylinder Geometry by Quasi-Separation of Variables. PLASMONICS (NORWELL, MASS.) 2014; 10:165-182. [PMID: 25620897 PMCID: PMC4295033 DOI: 10.1007/s11468-014-9791-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/25/2014] [Indexed: 06/04/2023]
Abstract
This paper describes the plasmonic modes in the parabolic cylinder geometry as a theoretical complement to the previous paper (J Phys A 42:185401) that considered the modes in the circular paraboloidal geometry. In order to identify the plasmonic modes in the parabolic cylinder geometry, analytic solutions for surface plasmon polaritons are examined by solving the wave equation for the magnetic field in parabolic cylindrical coordinates using quasi-separation of variables in combination with perturbation methods. The examination of the zeroth-order perturbation equations showed that solutions cannot exist for the parabolic metal wedge but can be obtained for the parabolic metal groove as standing wave solutions indicated by the even and odd symmetries.
Collapse
Affiliation(s)
- Kazuyoshi Kurihara
- Department of Physics, Faculty of Education and Regional Studies, University of Fukui, Fukui, 910-8507 Japan
| | - Akira Otomo
- Kobe Advanced ICT Research Center, National Institute of Information and Communications Technology (NICT), Kobe, 651-2492 Japan
| | - Kazuhiro Yamamoto
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka, 816-8580 Japan
| | - Junichi Takahara
- Graduate School of Engineering, Osaka University, 1-2 Yamadaoka, Suita, Osaka 565-0871 Japan
| | - Masahiko Tani
- Research Center for Development of Far-Infrared Region, University of Fukui, Fukui, 910-8507 Japan
| | - Fumiyoshi Kuwashima
- Department of Electrical, Electronics and Computer Engineering, Fukui University of Technology, Fukui, 910-8505 Japan
| |
Collapse
|
16
|
Liu S, Mitrofanov O, Nahata A. Transmission bleaching and coupling crossover in a split tapered aperture. OPTICS EXPRESS 2013; 21:30895-30902. [PMID: 24514662 DOI: 10.1364/oe.21.030895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigate the spectral transmission properties of conically tapered metallic apertures made in a split metallic plate using terahertz (THz) time-domain spectroscopy. The introduction of even a small gap between the two halves of the plate results in spectral broadening of the transmitted radiation due to a reduction of the cut-off effect. We find that the resulting transmission spectrum can be described as a weighted sum of the spectra associated with a tapered aperture and a parallel plate waveguide, with the gap spacing controlling the relative ratio. We further find that the field concentration properties of the aperture in a split plate are limited by the radiation leakage through the gap and propose a tapered shell structure to realize strong broadband field concentration. Using numerical simulations, we validate these observations and yield insight into the mode properties within the split tapered aperture.
Collapse
|
17
|
Liu S, Vardeny ZV, Nahata A. Concentration of broadband terahertz radiation using a periodic array of conically tapered apertures. OPTICS EXPRESS 2013; 21:12363-12372. [PMID: 23736454 DOI: 10.1364/oe.21.012363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We describe the optical concentration properties of periodic arrays of conically tapered metallic apertures measured using terahertz (THz) time-domain spectroscopy. As a first step in this process, we optimize the geometrical properties of individual apertures, keeping the output aperture diameter fixed, and find that the optimal taper angle is 30°. A consequence of increasing the taper angle is that the effective cutoff frequency red shifts, which can be readily explained using conventional waveguide theory. We then fabricate and measure the transmission properties of a periodic (hexagonal) array of optimized tapered apertures. In contrast to periodic arrays of subwavelength apertures in thin metal films, which are characterized by narrowband transmission resonances associated with the periodic spacing, here we observe broadband enhanced transmission above the effective cutoff frequency. Further enhancement in the concentration capabilities of the array can be achieved by tilting the apertures towards the array center, although the optical throughput of individual tapered apertures is reduced with increasing tilt angle. Finally, we discuss possible future directions that utilize cascaded structures, as a means for obtaining further enhancement in the amplitude of the transmitted THz radiation.
Collapse
Affiliation(s)
- Shuchang Liu
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112, USA
| | | | | |
Collapse
|