Characterization of SPR and Cavity Modes in 1D Gold Nanograting Chips: Figure of Merit Analysis and Implications for Raman Signal Enhancement

The optical properties of the 1D nanograting chip have been explored based on computational and experimental studies. From the results of dispersion curve analysis, cavity and SPR modes have been demonstrated by 1D nanograting chip with periods of 400 nm and 800 nm. In this grating period range, the cut-off period is at a grating period of 644 nm. Of the 2 investigated chips, the chip with a grating period of 800 nm is more promising for application as a dual-mode sensor based on SPR-Raman. By using the angle interrogation method, this chip has a FoM which is 3.43 times higher than the 1D nanograting chip with a period of 400 nm. In the same system, Raman measurements have also been performed using R6G as the standard material. The experimental results show that the Raman signal measured at the grating resonance angle shows higher intensity than the Raman measurement without the SPR sensor. SPR-induced electromagnetic enhancement plays an important role in amplifying Raman signals in SERS and this approach is very promising to be further developed to obtain sensors that are not only sensitive but also accurate.