Disk array-type plasmonic chip for fluorescence enhancement

Abstract Plasmonic chips are chip-type devices with wavelength-order periodic structures covered with metal based on grating-coupled surface plasmon resonance for sensitive detection. In this study, we investigated a disk-array-type (DA) structure, which is an inversion of the hole-array-type (HA) structure, to further improve the fluorescence enhancement. Increases in the dip depth in the reflection spectra and the corresponding field enhancement were observed for the DA structure, resulting in larger fluorescence enhancement than that of the HA structure. The relationship between the duty ratio, convex height, and enhancement factors was also investigated. The contribution of excitation enhancement was dominant and strongly correlated with dip depth, reaching a maximum at a convex height of 25 nm and a duty ratio of approximately 0.6. Furthermore, the excitation enhancements calculated by rigorous coupled wave analysis showed an optimal structure with the highest values.