Femtosecond Bessel beam induced ladder-like LIPSS on trimetallic surface for SERS-based sensing of Tetryl and PETN

Abstract

Laser-induced periodic surface structures (LIPSS) have emerged as a potential branch of nanophotonics, offering unparalleled applications in numerous other research fields such as on-chip microelectronics, hydrogen evolution, solar-energy conversion, photodetectors, photocatalysis, and sensing. In this study, for the first time, we have created novel, Ag-Au-Cu alloyed trimetallic, ladder-like LIPSS nanostructures engaging an axicon-generated femtosecond Bessel beam. The LIPSS formation mechanism through modulation of ablation fluence profile, involving interference of photon-induced surface plasmon polariton with incident beam, has been meticulously divulged. The overlapping feature of Bessel beam profiles has been considered to improve the coupling of electromagnetic modes with the pre-patterned surfaces. The period (Λ) of the fabricated low spatial frequency LIPSS has been estimated to be 540 ± 12 nm. Also, as a comparative study, the distinct topographical features of nanostructures generated under a Gaussian beam with an identical fluence has also been presented. Additionally, these trimetallic plasmonic nanostructures have demonstrated outstanding excellence as active surface-enhanced Raman scattering substrates for sensing applications. Traces (200 nM) of real-time explosives such as Tetryl and pentaerythritol tetranitrate (PETN) have been detected, while achieving enhancement factors in the range of 105, making these viable for practical applications.