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Sang Y, Wang CY, Raja SS, Cheng CW, Huang CT, Chen CA, Zhang XQ, Ahn H, Shih CK, Lee YH, Shi J, Gwo S. Tuning of Two-Dimensional Plasmon-Exciton Coupling in Full Parameter Space: A Polaritonic Non-Hermitian System. Nano Lett 2021; 21:2596-2602. [PMID: 33689382 DOI: 10.1021/acs.nanolett.1c00198] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Non-Hermitian photonic systems with gains and/or losses have recently emerged as a powerful approach for topology-protected optical transport and novel device applications. To date, most of these systems employ coupled optical systems of diffraction-limited dielectric waveguides or microcavities, which exchange energy spatially or temporally. Here, we introduce a diffraction-unlimited approach using a plasmon-exciton coupling (polariton) system with tunable plasmonic resonance (energy and line width) and coupling strength. By designing a chirped silver nanogroove cavity array and coupling a single tungsten disulfide monolayer with a large contrast in resonance line width, we show the tuning capability through energy level anticrossing and plasmon-exciton hybridization (line width crossover), as well as spontaneous symmetry breaking across the exceptional point at zero detuning. This two-dimensional hybrid material system can be applied as a scalable and integratable platform for non-Hermitian photonics, featuring seamless integration of two-dimensional materials, broadband tuning, and operation at room temperature.
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Affiliation(s)
- Yungang Sang
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Chun-Yuan Wang
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
- Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Soniya S Raja
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Chang-Wei Cheng
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Chiao-Tzu Huang
- Department of Electrophysics, National Chiao-Tung University, Hsinchu 30010, Taiwan
| | - Chun-An Chen
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Xin-Quan Zhang
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Hyeyoung Ahn
- Department of Photonics, National Chiao-Tung University, Hsinchu 30010, Taiwan
| | - Chih-Kang Shih
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Yi-Hsien Lee
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Jinwei Shi
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Shangjr Gwo
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Institute of NanoEngineering and Microsystems, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Department of Electrophysics, National Chiao-Tung University, Hsinchu 30010, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
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Wang CY, Sang Y, Yang X, Raja SS, Cheng CW, Li H, Ding Y, Sun S, Ahn H, Shih CK, Gwo S, Shi J. Engineering Giant Rabi Splitting via Strong Coupling between Localized and Propagating Plasmon Modes on Metal Surface Lattices: Observation of √N Scaling Rule. Nano Lett 2021; 21:605-611. [PMID: 33350840 DOI: 10.1021/acs.nanolett.0c04099] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We present a strong coupling system realized by coupling the localized surface plasmon mode in individual silver nanogrooves and propagating surface plasmon modes launched by periodic nanogroove arrays with varied periodicities on a continuous silver medium. When the propagating modes are in resonance with the localized mode, we observe a √N scaling of Rabi splitting energy, where N is the number of propagating modes coupled to the localized mode. Here, we confirm a giant Rabi splitting on the order of 450-660 meV (N = 2) in the visible spectral range, and the corresponding coupling strength is 160-235 meV. In some of the strong coupling cases studied by us, the coupling strength is about 10% of the mode energy, reaching the ultrastrong coupling regime.
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Affiliation(s)
- Chun-Yuan Wang
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Yungang Sang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Xinyue Yang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Soniya S Raja
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Chang-Wei Cheng
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Haozhi Li
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Yufeng Ding
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Shuoyan Sun
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Hyeyoung Ahn
- Department of Photonics, National Chiao-Tung University, Hsinchu 30010, Taiwan
| | - Chih-Kang Shih
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Shangjr Gwo
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Jinwei Shi
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
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Raja SS, Cheng CW, Gwo S. Low-loss aluminum epitaxial film for scalable and sustainable plasmonics: direct comparison with silver epitaxial film. Nanoscale 2020; 12:23809-23816. [PMID: 33237103 DOI: 10.1039/d0nr06603f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Aluminum is a plasmonic material well known for its excellent stability, complementary metal-oxide-semiconductor compatibility and wide availability as compared to popular plasmonic materials such as gold and silver. Aluminum can support surface plasmon resonances in a broad spectral range, including the deep ultra-violet, a regime where no other plasmonic materials can work. However, conventional aluminum films suffer from high losses in the visible region and low fidelity and reproducibility in nanofabrication, making aluminum plasmonics non-ideal for applications. Herein, we report the experimental results of consistent surface plasmon propagation length measurements for epitaxially grown aluminum and silver films (epifilms), using three different methods (white light interferometry, laser scattering and spectroscopic ellipsometry) in the full visible spectrum. In order to avoid losses caused by inferior material quality, we used single-crystalline aluminum and silver films for direct comparison. We found that, on directly comparing with the silver epifilm, the aluminum epifilm possesses reasonably long plasmon propagation lengths in the full visible range and outperforms silver in the deep blue region. These results illustrate the great potential of epitaxial aluminum films for visible-spectrum plasmonic applications, resulting from their superior crystallinity and excellent surface and interface properties.
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Affiliation(s)
- Soniya S Raja
- Institute of NanoEngineering and MicroSystems, National Tsing-Hua University, Hsinchu 30013, Taiwan.
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Raja SS, Cheng CW, Sang Y, Chen CA, Zhang XQ, Dubey A, Yen TJ, Chang YM, Lee YH, Gwo S. Epitaxial Aluminum Surface-Enhanced Raman Spectroscopy Substrates for Large-Scale 2D Material Characterization. ACS Nano 2020; 14:8838-8845. [PMID: 32589398 DOI: 10.1021/acsnano.0c03462] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive technique to identify vibrational fingerprints of trace analytes. However, present SERS techniques suffer from the lack of uniform, reproducible, and stable substrates to control the plasmonic hotspots in a wide spectral range. Here, we report the promising application of epitaxial aluminum films as a scalable plasmonic platform for SERS applications. To assess the uniformity of aluminum substrates, atomically thin transition metal dichalcogenide monolayers are used as the benchmark analyte due to their inherent two-dimensional homogeneity. Besides the distinctive spectral capability of aluminum in the ultraviolet (325 nm), we demonstrate that the aluminum substrates can even perform comparably with the silver counterparts made from single-crystalline colloidal silver crystals using the same SERS substrate design in the visible range (532 nm). This is unexpected from the prediction solely based on optical dielectric functions and illustrate the superior surface and interface properties of epitaxial aluminum SERS substrates.
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Affiliation(s)
- Soniya S Raja
- Institute of Nanoengineering and Microsystems, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Chang-Wei Cheng
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Yungang Sang
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- School of Physics, Peking University, Beijing 100871, China
| | - Chun-An Chen
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Xin-Quan Zhang
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Abhishek Dubey
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Ta-Jen Yen
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Yu-Ming Chang
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - Yi-Hsien Lee
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan
| | - Shangjr Gwo
- Institute of Nanoengineering and Microsystems, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan
- Center for Applied Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan
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