Enhanced circular dichroism of TDBC in a metallic hole array structure*

We investigate the enhanced chirality of chiral molecular J-aggregates (TDBC) by the propagating surface plasmons (PSPs) in the metallic hole array structure filled with TDBC. The two ends of the hole in the metal film form a low quality factor Fabry-Perot (FP) cavity, and this cavity confines PSPs. The resonant wavelength of the metallic hole array is tuned by the lattice constant and the size of the hole. Both the resonant wavelength of Ag hole array and the volume ratio of TDBC in the hybridized structure influence on the enhancement of the circular dichroism (CD) spectrum. The curve of CD spectrum shows Fano-like line-shape, due to the interaction between the non-radiative field in the FP cavity and the radiative field in chiral TDBC. The maximum of the CD spectrum of the hybridized structure is 0.025 times as the one of the extinction spectrum in a certain structure, while the maximum of the CD spectrum of TDBC is 1/3000 times as the one of the extinction spectrum. The enhanced factor is about 75. The resonant wavelength of the metallic hole array can be tuned in a large wavelength regime, and the chirality of a series of molecular J-aggregates with different resonant wavelengths can be enhanced. Our structure provides a new method to amplify the chirality of molecular J-aggregates in experiments.