Laser-induced periodic structures-assisted surface plasmon resonance refractive index sensor

Laser-induced periodic surface structures (LIPSS) offer a simple, single-step technique for creating periodic patterns on solids in an ambient air. Combined with metals like gold or silver, LIPSS enhances grating-assisted refractive index (RI) sensors using surface plasmon resonance (SPR). This study analyzes an SPR sensor in the Kretschmann configuration with a periodically modulated silver layer. The modulation is created by LIPSS formed on a titanium-coated glass prism using femtosecond laser pulses, followed by a silver coating. Reflection spectra for wavelengths λ = 600-1700 nm were calculated for various angles of incidence and RI values (1.33- 1.4). Unlike a flat sensor with a single resonance, the LIPSS-based sensor shows multiple resonances (λ = 1000-1700 nm) due to modes on inner and outer interfaces. LIPSS reduces resonance spectral width by an order of magnitude, but also reduces sensitivity similarly, weakly affecting the Figure of Merit. The LIPSS-assisted sensor was also tested experimentally.