Adaptive Gap-Tunable\nSurface-Enhanced Raman Spectroscopy

Abstract

Gap plasmon (GP) resonance in static surface-enhanced\nRaman spectroscopy\n(SERS) structures is generally too narrow and not tunable. Here, we\npresent an adaptive gap-tunable SERS device to selectively enhance\nand modulate different vibrational modes via active flexible Au nanogaps,\nwith adaptive optical control. The tunability of GP resonance is up\nto ∼1200 cm^–1 by engineering gap width, facilitated\nby mechanical bending of a polyethylene terephthalate substrate. We\nconfirm that the tuned GP resonance selectively enhances different\nRaman spectral regions of the molecules. Additionally, we dynamically\ncontrol the SERS intensity through the wavefront shaping of excitation\nbeams. Furthermore, we demonstrate simulation results, exhibiting\nthe mechanical and optical properties of a one-dimensional flexible\nnanogap and their advantage in high-speed biomedical sensing. Our\nwork provides a unique approach for observing and controlling the\nenhanced chemical responses with dynamic tunability.