Abstract
In this work, we demonstrate the strong extrinsic chirality of the larger-area metal nanocrescents by experiments and simulations. Our results show that the metal nanocrescent exhibits giant and tunable circular dichroism (CD) effect, which is intensively dependent on the incident angle of light. We attribute the giant extrinsic chirality of the metal nanocrescent to the excitation efficiencies difference of localized surface plasmon resonance (LSPR) modes for two kinds of circularly polarized light at a non-zero incident angle. In experiment, the largest CD of 0.37 is obtained at the wavelength of 826 nm with the incident angle of 60°. Furthermore, the CD spectra can be tuned flexibly by changing the metal nanocrescent diameter. Benefitting from the simple, low-cost and mature fabrication process, the proposed large-area metal nanocrescents are propitious to application.
Highlights
Chirality is a general property, which has taken an extremely important role in biology, chemistry, physics and medicine[1,2]
Zheludev and his collaborator observed circular dichroism (CD) effect in GHz region from an array of metal split rings induced by extrinsic chirality[21]
These plasmonic structures with strong extrinsic chiral effects are expected to develop some opportunities in application
Summary
Chirality is a general property, which has taken an extremely important role in biology, chemistry, physics and medicine[1,2]. Leon et al demonstrated experimentally and theoretically strong CD of the extrinsic chiral metasurface consisting of an array of gold split ring resonators[24] These plasmonic structures with strong extrinsic chiral effects are expected to develop some opportunities in application. The CD peaks appear near the frequency of LSPR bands Based on these results, we give a qualitative explanation for the giant extrinsic chirality of the metal nanocrescent, that at a non-zero incident angle θ, the excitation efficiencies of LSPR modes for the two kinds of circularly polarized light are different. Our low-cost large-area metal nanocrescents with giant and tunable CD stand a good chance to promote the practical application of chiral effect
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