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

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

机构地区：[1]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 [2]National Engineering Research Center for High Efficiency Grinding,College of Mechanical and Vehicle Engineering,Hunan University,Changsha 410082,China [3]Department of Chemistry and Biochemistry,University of California,Santa Barbara,California,93106,USA.

出　　处：《Opto-Electronic Advances》2021年第12期1-14,共14页光电进展（英文）

摘　　要：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 reson-ances 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 micro-scopy(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,en-abling boosting up the local field for both bands by multiscale coupling.With large field enhancements,multiband detec-tion 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.

关 键 词：optical antenna charge transfer plasmon multiband resonances scanning near-field optical microscopy surface-enhanced infrared spectroscopy 

分 类 号：TN820[电子电信—信息与通信工程]