科研之友
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摘要
Plasmonic metamolecules have many peculiar properties and have been applied in biological and materials science such as in reconfigurable 3D building blocks for complex nano-architectures and imaging probes for high-resolution sensing. In these applications, fast detection of the bond angles of the sub-wavelength metamolecules is highly desired. However, angle detection is not the same as orientation detection. The two orientations must be determined simultaneously, and common orientation sensors can only measure one. In this work, we propose and demonstrate a method to resolve the bond angle of a plasmonic metamolecule composed of three spherical nanoparticles. The detection of the bond angle is achieved via modulation depth analysis of polarization-resolved dark-field images. The underlying mechanism is found to be the opposing responses of the longitudinal and transversal bonding modes to the polarization variation of the incident light. In addition, the spectrally degenerate structures are further distinguished by the spot center localization method. This method may pave the way for practical application of plasmonic metamolecules.
