Femtosecond laser-ablated Fresnel zone plate fiber probe and sensing applications

We investigate the Fresnel zone plate (FZP) inscribed on multimode fiber endface using femtosecond laser ablation and its application in sensing. The mode transmission through fiber tips with FZP is investigated both by the beam propagation method theoretically and by measuring the beam images with a charge-coupled device camera experimentally, which show a good agreement. Such devices are tested for surface-enhanced Raman scattering (SERS) using the aqueous solution of rhodamine 6G under a Raman spectroscopy. The experimental results demonstrate that the SERS signal is enhanced benefiting from focal ability of FZP, which is a promising method for the particular biochemical spectra sensing applications.