Abstract
The chiroptical response of most naturally occurring chiral materials is generally very weak, which discourages further studies and limits applications. Recently, chiral plasmonic structures have received significant attention because of their large chiroptical response. Note that the interaction between the constituents is extremely important and indispensable to the chiroptical response in a chiral plasmonic system. Here, we extend the study of chiroptical response concerning the interaction between the constituents to a strong plasmon coupling regime based on the dimer of twisted metal nanorods. To this end, we realize the fabrication of twisted nanorods with a small gap size of ∼15 nm to ensure that we can observe the separated hybridized modes generated by the plasmon coupling between the twisted nanorods. The dependence of the plasmon coupling and dissymmetry factor on the gap size and twisted angle clearly demonstrates that the plasmon coupling followed by the hybridization strongly enhances the chiroptical response. The dissymmetry factor of the experimentally optimized structures reached values of up to ∼1.03, which is much larger than other nano-plasmonic systems of the same order of dimension. Furthermore, the chiroptical response, as well as the plasmon coupling, is very sensitive to the configuration of the structure, which means that they are precisely controlled by tuning the gap size and twisted angle. Our study that is based on the plasmon coupling provides a further understanding of the study of chiroptical response and will assist in the future design and improvement of chiral plasmonic structures for metamaterial applications.
Highlights
Chiral objects are objects that cannot be superimposed onto their mirror image
To gain further insight into the relationship between the g factor and the plasmon coupling in our system, we summarized the experimental results in Figs. 4(c) and 4(f), which illustrate how the maximum value of the g factor changes with the strength of the plasmon coupling between the twisted nanorods
We studied the chiroptical response of a dimer of twisted metal nanorods concerning the plasmon coupling
Summary
Chirality is common in nature and reflects a fundamental property of materials. Many biomolecules, such as amino acids, nucleotides, and sugars, are inherently chiral. A chiral material can exhibit a chiroptical response via the different absorption of left- and right-handed circularly polarized light. Where Alabs and Arabs are the absorption cross sections for the left- and right-handed circularly polarized light, respectively. This chiroptical phenomenon is of great significance in fundamental research and has successfully been utilized in many different fields.[5,6,7] The value of g factor is within the range of −2 to +2. The chiroptical response is inherently weak for most naturally occurring chiral materials with the g factor smaller than 10−3 due to the small size of molecules,[8,9] which discourages further investigations and limits applications
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