Directional propagation and enhanced emission of chiral light manipulated by gold helices

Abstract

Nanoplasmonic waveguides have been demonstrated to own unique advantages in controlling the directionality of nanoscale chiral light sources. They could facilitate the directional propagation of chiral light, enhance electromagnetic field localization, and significantly amplify light–matter interaction intensities. Notably, gap plasmon structures with asymmetric geometries exhibit a remarkable degree of directional coupling. However, due to divergence loss in dielectric waveguides, achieving long-distance directional light transmission remains challenging. In this work, we have fabricated gold helices with sharp tips and spiral grooves, forming a gap plasmon nanostructure incorporating a gold helix. Then, through Raman spectroscopy and finite-difference time-domain method, we have systematically investigated the asymmetric directional propagation of chiral light in this nanostructure. The gold helices exhibit a pronounced Raman scattering signal, resulting in the augmented optical signal enhancement effect. Moreover, the gap plasmon nanostructure significantly enhances the emission intensity and the transmission distance of light, which enables precise control over the directional propagation of chiral light. These findings hold significant potential for improving the emission intensity of chiral light, which is crucial for information transmission and chip-based information processing.