[17p-A404-1~14] 3.16 Optics and Photonics English Session

▲ [17p-A404-8] Strong Local Optical Chirality of Chiral Plasmonic Nanostructures under Linearly Polarized Excitation

〇(P)Khai Quang Le¹, Hiromi Okamoto^1,2 (1.Institute for Molecular Science, 2.The Graduate University for Advanced Studies (Sokendai))

Keywords:Chiral plasmonic nanostructure, Optical chirality, Photoluminescence enhancement dissymmetry

Recently, we experimentally observed a strong dissymmetry (g>0.1) between left- and right-handed circularly polarized dye fluorescence enhancement (FLE) induced by chiral plasmonic nanostructures upon linearly polarized excitation. We used IR125 dye as a fluorescent emitter with luminescence that was enhanced by its near-field interaction with the chiral plasmon. The FLE dissymmetry spectra showed maximum amplitudes at 800-850 nm, which correspond approximately to the wavelength providing maximal extinction dissymmetry (~800 nm) of the plasmonic nanostructure. In this work, physics behind the FLE dissymmetry is elucidated via electromagnetic model analysis. The sketch of the model is illustrated in Fig. 1(a). Electric field enhancements and optical chiralities evaluated at 5 nm above the nanostructure surface under x- and y-polarized excitations are shown in Figs. 1(b,c) and (d,e), respectively. We revealed that y-polarized excitation provided stronger near-field enhancement around the corners of the nanostructures and optical chirality than that of x-polarized excitation. The dissymmetry is resonant with a longitudinal (y-polarized) chiral multipolar plasmon mode whereas it is relatively small at the wavelength resonant with a dipolar transverse (x-polarized) plasmon mode. The achiral IR125 dye molecules attached on the chiral nanostructures are considered to yield circularly polarized luminescence.