Circularly Polarized Photoluminescence from Achiral Dye Molecules Induced by Plasmonic Two-Dimensional Chiral Nanostructures

We report strong dissymmetry between left- and right-handed circularly polarized photoluminescence (PL) enhancement induced by 2D chiral gold nanostructures, which can be utilized to provide a circularly polarized luminescence source. Lightning-bolt-like (composed of two displaced rectangles) chiral plasmonic gold nanostructures were fabricated on a glass substrate and were adopted as materials to induce dissymmetry in PL enhancement. We employed achiral IR125 dye as an achiral molecular PL emitter with luminescence that was enhanced by near-field interaction between the chiral plasmon and the molecule. PL decay measurements confirmed that the PL enhancement arose from the plasmonic effect. Large PL enhancement dissymmetry factors g > 0.1 were obtained in the wavelength region near 800 nm. The dissymmetry of PL enhancement showed maximum amplitudes at 800-850 nm, which approximately correspond to the wavelength providing maximal extinction dissymmetry (similar to 800 nm), and is resonant with a chiral multipolar plasmon mode. The dissymmetry was relatively small at the wavelength resonant with a dipolar plasmon mode.