Dual-resonance 1 D metallic gratings detecting rhodamine 6G molecules at concentrations down to 10⁻⁹ mol/L

The development of low-cost, large-area ordered plasma surfaces is crucial for surface-enhanced Raman spectroscopy (SERS). Due to their periodic structure, gratings offer strong optical tunability and uniform SERS enhancement, making them a popular substrate. This study employs holographic lithography to fabricate high aspect ratio one-dimensional metallic gratings that can simultaneously excite propagating surface plasmon polaritons and Fabry-Pérot resonances. By adjusting the grating parameters, we achieved significant enhancement of the electromagnetic field. Using Rhodamine 6G (R6G) as a probe, we detected concentrations as low as 10⁻⁹ mol/L for the first time with 1D gratings, demonstrating good uniformity at 10⁻⁷ mol/L. This validates the high sensitivity and uniformity of our SERS substrate. The cost-effective manufacturing process and high performance of these gratings provide a novel approach to the commercialization of SERS substrates.