Amplification of Surface-Enhanced Raman Scattering in Photonic Crystal Fiber Using Offset Launch Method

In this paper, we report the amplification effect of surface-enhanced Raman scattering (SERS) in a solid-core photonic crystal fiber. Gold nanoparticles (AuNPs) are self-assembled on the inner walls of the cladding air holes through a multilayered deposition procedure. Offset launch method is for the first time employed to introduce extra enhancement in the intensity of SERS signals, as compared to the conventional core launch method. A theoretical analysis on modal field distribution for both launching conditions is carried out to account for such improvement. It shows that by adjusting the launching position of laser beam from the solid fiber core to an air hole in the cladding, overlap of the excited mode with AuNPs has been increased significantly. The SERS probe is demonstrated to achieve a detection limit as low as 10 −7 M in concentration, which shows a competitive performance for molecule analysis.