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Chen R, Zheng Y, Huang X, Lin Q, Ye C, Xiong M, Wubs M, Ma Y, Pu M, Xiao S. Observation of multiple bulk bound states in the continuum modes in a photonic crystal cavity. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2023; 14:544-551. [PMID: 37152473 PMCID: PMC10155626 DOI: 10.3762/bjnano.14.45] [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: 12/25/2022] [Accepted: 04/18/2023] [Indexed: 05/09/2023]
Abstract
Obtaining bound states in the continuum (BICs) in photonic crystals gives rise to the realization of resonances with high quality factors for lasing and nonlinear applications. For BIC cavities in finite-size photonic crystals, the bulk resonance band turns into discrete modes with different mode profiles and radiation patterns. Here, photonic-crystal BIC cavities encircled by the photonic bandgap of lateral heterostructures are designed. The mirror-like photonic bandgap exhibits strong side leakage suppression to confine the mode profile in the designed cavity. Multiple bulk quantized modes are observed both in simulation and experiment. After exciting the BIC cavity at different positions, different resonance peaks are observed. The physical origin of the dependence between the resonance peak and the illuminating position is explained by analyzing the mode profile distribution and further verified by numerical simulations. Our findings have potential applications regarding the mode selectivity in BIC devices to manipulate the lasing mode in photonic-crystal surface-emitting lasers or the radiation pattern in nonlinear optics.
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Affiliation(s)
- Rui Chen
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
- State Key Lab of Modern Optical Instrumentation, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou 310058, China
| | - Yi Zheng
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Xingyu Huang
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Qiaoling Lin
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
- NanoPhoton – Center for Nanophotonics, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Chaochao Ye
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Meng Xiong
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
- NanoPhoton – Center for Nanophotonics, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Martijn Wubs
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
- NanoPhoton – Center for Nanophotonics, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Yungui Ma
- State Key Lab of Modern Optical Instrumentation, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou 310058, China
| | - Minhao Pu
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Sanshui Xiao
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
- NanoPhoton – Center for Nanophotonics, Technical University of Denmark, Kgs. Lyngby, Denmark
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Lebsir Y, Boroviks S, Thomaschewski M, Bozhevolnyi SI, Zenin VA. Ultimate Limit for Optical Losses in Gold, Revealed by Quantitative Near-Field Microscopy. NANO LETTERS 2022; 22:5759-5764. [PMID: 35787133 DOI: 10.1021/acs.nanolett.2c01059] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We report thorough measurements of surface plasmon polaritons (SPPs) running along nearly perfect air-gold interfaces formed by atomically flat surfaces of chemically synthesized gold monocrystals. By means of amplitude- and phase-resolved near-field microscopy, we obtain their propagation length and effective mode index at visible wavelengths (532, 594, 632.8, 729, and 800 nm). The measured values are compared with the values obtained from the dielectric functions of gold that are reported in literature. Importantly, a reported dielectric function of monocrystalline gold implies ∼1.5 times shorter propagation lengths than those observed in our experiments, whereas a dielectric function reported for properly fabricated polycrystalline gold leads to SPP propagation lengths matching our results. We argue that the SPP propagation lengths measured in our experiments signify the ultimate limit of optical losses in gold, encouraging further comprehensive characterization of optical material properties of pure gold as well as other plasmonic materials.
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Affiliation(s)
- Yonas Lebsir
- Centre for Nano Optics, University of Southern Denmark, 5230 Odense, Denmark
- Institute for Experimental and Applied Physics, Kiel University, 24118 Kiel, Germany
| | - Sergejs Boroviks
- Centre for Nano Optics, University of Southern Denmark, 5230 Odense, Denmark
- Nanophotonics and Metrology Laboratory (NAM), Swiss Federal Institute of Technology in Lausanne (EPFL), 1015 Lausanne, Switzerland
| | | | - Sergey I Bozhevolnyi
- Centre for Nano Optics, University of Southern Denmark, 5230 Odense, Denmark
- Danish Institute for Advanced Study, University of Southern Denmark, 5230 Odense, Denmark
| | - Vladimir A Zenin
- Centre for Nano Optics, University of Southern Denmark, 5230 Odense, Denmark
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Extremely confined gap plasmon modes: when nonlocality matters. Nat Commun 2022; 13:3105. [PMID: 35661728 PMCID: PMC9166740 DOI: 10.1038/s41467-022-30737-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 05/09/2022] [Indexed: 11/14/2022] Open
Abstract
Historically, the field of plasmonics has been relying on the framework of classical electrodynamics, with the local-response approximation of material response being applied even when dealing with nanoscale metallic structures. However, when the confinement of electromagnetic radiation approaches atomic scales, mesoscopic effects are anticipated to become observable, e.g., those associated with the nonlocal electrodynamic surface response of the electron gas. Here, we investigate nonlocal effects in propagating gap surface plasmon modes in ultrathin metal–dielectric–metal planar waveguides, exploiting monocrystalline gold flakes separated by atomic-layer-deposited aluminum oxide. We use scanning near-field optical microscopy to directly access the near-field of such confined gap plasmon modes and measure their dispersion relation via their complex-valued propagation constants. We compare our experimental findings with the predictions of the generalized nonlocal optical response theory to unveil signatures of nonlocal damping, which becomes appreciable for few-nanometer-sized dielectric gaps. When approaching atomic-scale confinement of the electromagnetic radiation nonlocal effects are not negligible. Here the authors approach that regime, probing extremely confined gap plasmon modes by means of scanning near-field optical microscopy, and suggesting that quantum nonlocal corrections should be taken into account.
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