12 September 2014 Effect of layered composite meta-structures on the optical activity and ellipticity of structural biomolecules
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Abstract
In this paper, we design layered composite meta-structures to investigate its’ effect on the optical activity and circular dichroism (CD). The layered composite meta-structures consist of thin gammadion nanostructure with thickness λ/10, where λ is the incident wavelength. The layered meta-structures are alternate between a dielectric and gold (AU) material. Each layered composite meta-gammadion is arranged together in an array of pitch 700 nm. In the first case, 3 layers of meta-gammadion, with metal-insulator-metal (MIM) and insulator-metal-insulator (IMI) configuration are simulated with material properties from optical hand book. There are 3 modes in the CD spectrum, which can be characterized into Bloch CD mode and hybrid CD modes. Compared with the CD spectrum of whole structure of gammadion in gold with same total height, the CD of the MIM layered composite are larger. When the number layer increase to 5, it is observed that the CD is reduced by 30% and there is a red shift in the Bloch CD mode and a slight blue shift in the hybrid CD modes. By further increasing the number of layers to 7, we observed further CD increment and larger wavelength shift in the CD modes. The layered composite meta-gammadion is fabricated using template stripping method. Experimental results also show excellent agreement with the simulation results for CD and wavelength shift. We submerge the layered meta-gammadion into a solution of chiral molecules. The CD spectrum of the meta-gammadion shows a larger wavelength shift compared to pure metal structures. This indicate a more sensitive and robust detection of chiral molecules.
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E. H. Khoo, E. H. Khoo, Y. Li Hor, Y. Li Hor, Eunice S. P. Leong, Eunice S. P. Leong, Y. J. Liu, Y. J. Liu, } "Effect of layered composite meta-structures on the optical activity and ellipticity of structural biomolecules", Proc. SPIE 9160, Metamaterials: Fundamentals and Applications 2014, 91601G (12 September 2014); doi: 10.1117/12.2061492; https://doi.org/10.1117/12.2061492
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