Nanobridged rhombic antennas supporting both dipolar and high-order plasmonic modes with spatially superimposed hotspots in the mid-infrared

En-Ming You; Yiqin Chen; Jun Yi; Zhao-Dong Meng; Qian Chen; Song-Yuan Ding; Huigao Duan; Martin Moskovits; Zhong-Qun Tian

doi:10.29026/oea.2021.210076

Opto-Electronic Advances (Dec 2021)

Nanobridged rhombic antennas supporting both dipolar and high-order plasmonic modes with spatially superimposed hotspots in the mid-infrared

En-Ming You,
Yiqin Chen,
Jun Yi,
Zhao-Dong Meng,
Qian Chen,
Song-Yuan Ding,
Huigao Duan,
Martin Moskovits,
Zhong-Qun Tian

Affiliations

En-Ming You: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
Yiqin Chen: National Engineering Research Center for High Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China
Jun Yi: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
Zhao-Dong Meng: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
Qian Chen: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
Song-Yuan Ding: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
Huigao Duan: National Engineering Research Center for High Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China
Martin Moskovits: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, 93106, USA
Zhong-Qun Tian: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China

DOI: https://doi.org/10.29026/oea.2021.210076
Journal volume & issue: Vol. 4, no. 12
pp. 1 – 14

Abstract

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Mid-infrared antennas (MIRAs) support highly-efficient optical resonance in the infrared, enabling multiple applications, such as surface-enhanced infrared absorption (SEIRA) spectroscopy and ultrasensitive mid-infrared detection. However, most MIRAs such as dipolar-antenna structures support only narrow-band dipolar-mode resonances while high-order modes are usually too weak to be observed, severely limiting other useful applications that broadband resonances make possible. In this study, we report a multiscale nanobridged rhombic antenna (NBRA) that supports two dominant resonances in the MIR, including a charge-transfer plasmon (CTP) band and a bridged dipolar plasmon (BDP) band which looks like a quadruple resonance. These assignments are evidenced by scattering-type scanning near-field optical microscopy (s-SNOM) imaging and electromagnetic simulations. The high-order mode only occurs with nanometer-sized bridge (nanobridge) linked to the one end of the rhombic arm which mainly acts as the inductance and the resistance by the circuit analysis. Moreover, the main hotspots associated with the two resonant bands are spatially superimposed, enabling boosting up the local field for both bands by multiscale coupling. With large field enhancements, multiband detection with high sensitivity to a monolayer of molecules is achieved when using SEIRA. Our work provides a new strategy possible to activate high-order modes for designing multiband MIRAs with both nanobridges and nanogaps for such MIR applications as multiband SEIRAs, IR detectors, and beam-shaping of quantum cascade lasers in the future.

Published in Opto-Electronic Advances

ISSN: 2096-4579 (Print)
Publisher: Institue of Optics and Electronics, Chinese Academy of Sciences
Country of publisher: China
LCC subjects: Science: Physics: Optics. Light
Website: http://www.oejournal.org/oea

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