| Summary: | 碩士 === 國立交通大學 === 光電工程研究所 === 103 === We propose a novel hybrid plasmonic nanostructure, rod-dimer/ring (RDR). The nanorod is regarded as a bridge pulling the charges from nanoring to nanorod, which induces large near-field in the gap region for its coupling effect and lightning effect. Besides, RDR can spread the field to the environment due to its open structure. Thus, optical properties of RDR are particularly suitable for relevant sensing applications.
From the experimental and simulated results, we found that there are two dominant modes, symmetric mode and anti-symmetric mode. We specifically paid attention to the symmetric mode because it obtained stronger dipole moment, thereby gaining stronger field intensity. Besides, the plasmonic behaviors of RDR are dependent on the structural geometry such as gap distance, rod width, and outer ring radius. These results indicate that the plasmonic behaviors of RDR possesses high tunable ability. In the trapping simulation, the optical force is up to 10.894 nN/W to trap 20 nm polystyrene particle under the excitation at 1.58 μm wavelength. We also successfully trapped 1 μm polystyrene in experiment. Meanwhile, the sensitivity of 634 nm/RIU in bulk media sensing was be observed. Via structure optimization of RDR with extremely large field intensity in environment, we expect that it has more potential in trapping and sensing applications.
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