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Plasmon-phonon coupling between metamaterials and molecular vibrations provides a new path for studying mid-infrared light-matter interactions and molecular detection. So far, the coupling between the plasmonic resonances of metamaterials and the phonon vibrational modes of molecules has been realized under linearly polarized light. Here, mid-infrared chiral plasmonic metasurfaces with high circular dichroism (CD) in absorption over 0.65 in the frequency range of 50 to 60 THz are demonstrated to strongly interact with the phonon vibrational resonance of polymethyl methacrylate (PMMA) molecules at 52 THz, under both left-handed and right-handed circularly polarized (LCP and RCP) light. The mode splitting features in the absorption spectra of the coupled metasurface-PMMA systems under both circular polarizations are studied in PMMA layers with different thicknesses. The relation between the mode splitting gap and the PMMA thickness is also revealed. The demonstrated results can be applied in areas of chiral molecular sensing, thermal emission, and thermal energy harvesting.
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Degenerate quasi-normal mode theory for near-field radiation between plasmonic structures
Near-field radiation can exceed the blackbody radiation limit due to the contributions from evanescent waves. One promising approach to further enhance near-field radiation beyond existing bulk materials is to utilize metamaterials or metasurfaces made from subwavelength plasmonic structures. In this work, we investigate the near-field thermal radiation between complex plasmonic structures with higher-order symmetry and degeneracy, which is crucial for understanding the radiative heat exchange between metamaterials or metasurfaces at extremely small gaps. We demonstrate that the introduction of degeneracy can drastically boost near-field thermal radiation between plasmonic structures. The enhancement of near-field thermal radiation originates from the emergence of degenerate resonance modes and the secondary emission of thermal photons due to the nonzero coupling between the degenerate modes. Our study provides new pathways for designing high-intensity near-field thermal emitters and absorbers for thermophotovoltaics, thermal management, and infrared spectroscopy.
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- Award ID(s):
- 1931964
- PAR ID:
- 10199504
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 28
- Issue:
- 23
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 34123
- Size(s):
- Article No. 34123
- Sponsoring Org:
- National Science Foundation
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