Femtosecond Single‐ and Double‐Pulse Fabrication of Periodic Nanostructures on Stainless Steel for Surface‐Enhanced Raman Spectroscopy

Fabrication of laser‐induced periodic surface structures (LIPSS) with near‐submicron length scale can greatly modify the surface‐related properties of materials as shown over the past decade. The hydrophobic properties can be combined with the dense nanostructures present in LIPSS to act as hotspots for highly sensitive surface‐enhanced Raman spectroscopy (SERS) applications. In this study, usage of single and double fs laser pulse irradiation to obtain different morphologies of LIPSS is demonstrated. By controlling the polarization, fluency, and interpulse delay between fs pulses, 1D and 2D periodic nanostructures are generated on 304‐stainless‐steel substrates, and the corresponding formation mechanisms are discussed. The LIPSS‐based sensors exhibit a high contact angle of 112°, demonstrating good capability of depositing analyte molecules after evaporation for SERS detection. Furthermore, the dense hotspots present in LIPSS‐based SERS sensors can detect up to 10 −10 M concentration of Rhodamine 6G with an analytical enhancement factor of 2 × 10 7 . The substrates also demonstrated uniform and repeatable measurements with an RSD of 9.64%. The results provide insight into controlling laser‐induced submicron morphology by changing experimental parameters as a simple and cost‐effective approach for ultra‐trace detection of molecules.