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Feng Z, Tan W, Jin Z, Chen YJ, Zhong Z, Zhang L, Sun S, Tang J, Jiang Y, Wu PH, Cheng J, Miao B, Ding H, Wang D, Zhu Y, Guo L, Shin S, Ma GH, Hou D, Huang SY. Anomalous Nernst Effect Induced Terahertz Emission in a Single Ferromagnetic Film. NANO LETTERS 2023; 23:8171-8179. [PMID: 37638840 DOI: 10.1021/acs.nanolett.3c02320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/29/2023]
Abstract
Despite its important role in understanding ultrafast spin dynamics and revealing novel spin/orbit effects, the mechanism of the terahertz (THz) emission from a single ferromagnetic nanofilm upon a femtosecond laser pump still remains elusive. Recent experiments have shown exotic symmetry, which is not expected from the routinely adopted mechanism of ultrafast demagnetization. Here, by developing a bidirectional pump-THz emission spectroscopy and associated symmetry analysis method, we set a benchmark for the experimental distinction of the THz emission induced by various mechanisms. Our results unambiguously unveil a new mechanism─anomalous Nernst effect (ANE) induced THz emission due to the ultrafast temperature gradient created by a femtosecond laser. Quantitative analysis shows that the THz emission exhibits interesting thickness dependence where different mechanisms dominate at different thickness ranges. Our work not only clarifies the origin of the ferromagnetic-based THz emission but also offers a fertile platform for investigating the ultrafast optomagnetism and THz spintronics.
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Affiliation(s)
- Zheng Feng
- Microsystem & Terahertz Research Center, CAEP, Chengdu 610200, P. R. China
| | - Wei Tan
- Microsystem & Terahertz Research Center, CAEP, Chengdu 610200, P. R. China
| | - Zuanming Jin
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, P. R. China
| | - Yi-Jia Chen
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Zhangfeng Zhong
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
| | - Liang Zhang
- Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China
- Department of Mechanical Engineering, National University of Singapore, 117516 Singapore
| | - Song Sun
- Microsystem & Terahertz Research Center, CAEP, Chengdu 610200, P. R. China
| | - Jin Tang
- School of Physics and Optoelectronics Engineering Science, Anhui University, Hefei 230601, P. R. China
| | - Yexing Jiang
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, P. R. China
| | - Po-Hsun Wu
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Jun Cheng
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
| | - Bingfeng Miao
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Haifeng Ding
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Dacheng Wang
- Microsystem & Terahertz Research Center, CAEP, Chengdu 610200, P. R. China
| | - Yiming Zhu
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, P. R. China
| | - Liang Guo
- Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China
| | - Sunmi Shin
- Department of Mechanical Engineering, National University of Singapore, 117516 Singapore
| | - Guo-Hong Ma
- Department of Physics, Shanghai University, Shanghai 200444, P. R. China
| | - Dazhi Hou
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
- Department of Physics, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Ssu-Yen Huang
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
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Cheng G, Si L, Shen Q, Niu R, Yuan Q, Bao X, Sun H, Ding J. Transmissive Pancharatnam-Berry metasurfaces with stable amplitude and precise phase modulations using dartboard discretization configuration. OPTICS EXPRESS 2023; 31:30815-30831. [PMID: 37710616 DOI: 10.1364/oe.501702] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 08/23/2023] [Indexed: 09/16/2023]
Abstract
Metasurfaces are ultra-thin artificial structures capable of flexibly manipulating electromagnetic (EM) waves. Among various applications, phase modulation of electromagnetic (EM) waves using metasurfaces holds great significance. The Pancharatnam-Berry (P-B) metasurfaces provides a complete 2π phase modulation by simply rotating the meta-atom. However, the fixed lattice in rotation employed by traditional P-B metasurfaces often results in unstable amplitude and imprecise P-B phase, leading to performance degradation. In this work, we demonstrate transmissive P-B metasurfaces with stable amplitude and precise phase modulation. To ensure stable amplitude and precise P-B phase, we adopt a dartboard discretization configuration with a hexagonal lattice for the meta-atom design. By applying topology optimization to the encoding sequence formed by surface pixels and dimensions, we significantly enhancing the high transmissive bandwidth of the optimized meta-atom. Furthermore, the optimized meta-atom exhibits a stable amplitude and precise P-B phase for each rotation angle. As proof-of-concept demonstrations, two metasurfaces for single and multiplexed vortex beams generating are designed utilizing the optimized meta-atom. Both the simulated and measured results indicate high mode purity of generated vortex beams. The design method can also be readily extended to other high performance metasurfaces with stable amplitude and precise phase manipulations, which can enhance the efficiency and capacity of metasurface-assisted holographic imaging and 6 G wireless communication systems.
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Sideris S, Zixian H, McDonnell C, Li G, Ellenbogen T. Holographic THz Beam Generation by Nonlinear Plasmonic Metasurface Emitters. ACS PHOTONICS 2023; 10:2972-2979. [PMID: 37602295 PMCID: PMC10436349 DOI: 10.1021/acsphotonics.3c00775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Indexed: 08/22/2023]
Abstract
The advancement of terahertz (THz) technology hinges on the progress made in the development of efficient sources capable of generating and shaping the THz emission. However, the currently available THz sources provide limited control over the generated field. Here, we use near-field interactions in nonlinear Pancharatnam-Berry phase plasmonic metasurfaces to achieve deep subwavelength, precise, and continuous control over the local amplitude of the emitted field. We show that this new ability can be used for holographic THz beam generation. Specifically, we demonstrate the generation of precisely shaped Hermite-Gauss, Top-Hat, and triangular beams. We show that using this method, higher-order modes are completely suppressed, indicating optimal nonlinear diffraction efficiency. In addition, we demonstrate the application of the generated structured beams for obtaining enhanced imaging resolution and contrast. These demonstrations hold immense potential to address challenges associated with a broad range of new applications employing THz technology.
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Affiliation(s)
- Symeon Sideris
- Department
of Physical Electronics, School of Electrical Engineering, Tel-Aviv University, Tel Aviv 6997801, Israel
- Center
for Light-Matter Interaction, Tel-Aviv University, Tel-Aviv 6779801, Israel
| | - Hu Zixian
- Department
of Materials Science and Engineering, Southern
University of Science and Technology, Shenzhen 518055, China
| | - Cormac McDonnell
- Department
of Physical Electronics, School of Electrical Engineering, Tel-Aviv University, Tel Aviv 6997801, Israel
- Center
for Light-Matter Interaction, Tel-Aviv University, Tel-Aviv 6779801, Israel
| | - Guixin Li
- Department
of Materials Science and Engineering, Southern
University of Science and Technology, Shenzhen 518055, China
- Institute
for Applied Optics and Precision Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Tal Ellenbogen
- Department
of Physical Electronics, School of Electrical Engineering, Tel-Aviv University, Tel Aviv 6997801, Israel
- Center
for Light-Matter Interaction, Tel-Aviv University, Tel-Aviv 6779801, Israel
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Boland JL, Damry DA, Xia CQ, Schönherr P, Prabhakaran D, Herz LM, Hesjedal T, Johnston MB. Narrowband, Angle-Tunable, Helicity-Dependent Terahertz Emission from Nanowires of the Topological Dirac Semimetal Cd 3As 2. ACS PHOTONICS 2023; 10:1473-1484. [PMID: 37215322 PMCID: PMC10197169 DOI: 10.1021/acsphotonics.3c00068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Indexed: 05/24/2023]
Abstract
All-optical control of terahertz pulses is essential for the development of optoelectronic devices for next-generation quantum technologies. Despite substantial research in THz generation methods, polarization control remains difficult. Here, we demonstrate that by exploiting band structure topology, both helicity-dependent and helicity-independent THz emission can be generated from nanowires of the topological Dirac semimetal Cd3As2. We show that narrowband THz pulses can be generated at oblique incidence by driving the system with optical (1.55 eV) pulses with circular polarization. Varying the incident angle also provides control of the peak emission frequency, with peak frequencies spanning 0.21-1.40 THz as the angle is tuned from 15 to 45°. We therefore present Cd3As2 nanowires as a promising novel material platform for controllable terahertz emission.
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Affiliation(s)
- Jessica L. Boland
- Photon
Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, U.K.
| | - Djamshid A. Damry
- Photon
Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, U.K.
| | - Chelsea Q. Xia
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Piet Schönherr
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Dharmalingam Prabhakaran
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Laura M. Herz
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Thorsten Hesjedal
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Michael B. Johnston
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
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