Vertical split-ring resonator based nanoplasmonic sensor

Abstract

Split-ring resonators (SRRs) have been the subject of investigation as plasmonic sensors that operate by sensing plasmon resonance shift δλ when exposed to a medium with a refractive index change δn. However, conventional planar SRRs have their plasmon fields spread into the substrates, reducing accessible sensing volume and its sensing performance. Such a limitation can be eradicated with vertical SRRs in which the plasmon fields localized in SRR gaps are lifted off from the substrate, allowing for greatly enhanced sensitivity. Here, we demonstrate the highest sensitivity among reported SRR-based sensors in optical frequencies. The authors acknowledge financial support from Ministry of Science and Technology, Taiwan (Grant Nos. 103-2745-M-002-004-ASP, 102-2745-M-002-005-ASP, 102-2911-I-002-505, 100-2112-M-019-003-MY3, and 100-2923-M-002-007-MY3) and Academia Sinica (Grant No. AS-103-TP-A06). They are also grateful to National Center for Theoretical Sciences, Taipei Office, Molecular Imaging Center of National Taiwan University, National Center for High-Performance Computing, Taiwan, and Research Center for Applied Sciences, Academia Sinica, Taiwan for their support. G. Sun acknowledges support from the Air Force Office of Scientific Research (Grant No. FA9550-14-1-0196, Dr. Gernot Pomrenke, Program Manager).