Dual Local Field Effects Modulate Incident Light for Amplifying SERS Hotspots Generation and Expanding Raman Enhancement Effective Range

Surface‐enhanced Raman scattering (SERS) demonstrates remarkable sensitivity and specificity in biosensing applications. However, attempts to improve SERS performance by fabricating metal nanostructures with sharper hotspot structures have encountered bottleneck, as the extremely short SERS effective distance remains unresolved. Here, a strategy to modulate SERS hotspots by additional long‐range local field effect is proposed. Stable opal photonic crystal (OPC) is developed for Au deposition, which modulates the incident light field directly, rather than merely optimizing the metal nanostructure, thereby significantly enhancing the hotspots generation. OPC substrate introduces structural discreteness to the deposited Au layer, also effectively improving hotspots intensity. Au layer prepared by direct evaporation can detect signal molecules with adsorption concentration of 10−9 m. The SERS properties of identical Au nanostructures are further enhanced 66.8 times by OPC effect. The coupling between OPC effect and localized surface plasmon resonance (LSPR) effect induces strong elastic scattering of incident photons over a large range, substantially enhancing Raman scattering 300 nm away from the substrate surface, facilitating the detection of larger‐sized objects. Dual‐local field effect modulating both the LSPR effect and incident photons, significantly enhances the SERS performance of identical metal nanostructures, offering broader effective range compared to conventional strategies, providing an effective approach for practical application.