Comparative analysis on Raman enhancement properties of waveguide coupled SERS probe

A waveguide structure with two air holes is used as surface-enhanced Raman scattering (SERS) probe. Raman scattering signal collected via waveguide coupled and free space ways is completely analyzed with optical Green function and quantum optics method. The parameters including averaged enhancement factor (AEF) and waveguide collection efficiency are discussed. The corresponding optical mode analysis is carried on with COMSOL solution. Prepared Ag nanoparticles and R6G (Rhodamine 6G) are filled into the air holes with vacuum pressure method. Experiments on different R6G concentrations, different fiber lengths, and different Ag densities are carried on to investigate the properties of the fiber SERS probe. Comparative discussion confirms a detection limit of 10^-15 M, an enhancement factor of 10⁸, and a sample of 8 cm length and volume ratio of 1:6 (Ag: R6G) having the best performance.