基于光纤渐逝波原理，结合表面增强拉曼散射（surface-enhanced Raman scattering,SERS）技术，实验研究一种银溶胶涂覆的2×2熔锥光纤的SERS特性.熔锥光纤由一对单模光纤经过熔融拉制而成，固化在其表面的银溶胶为表面活性基底，起拉曼增强作用.随着锥区长度的增加，纤芯逐渐减小，其对光的束缚能力变弱，从而透射出较强的可作为拉曼激发光源的渐逝波.实验中，以R6G为待测溶液，在耦合锥区探测到低浓度目标分子R6G的拉曼光谱，其最低检测浓度达到了10^-8 mol/L.

Based on the optical fiber evanescent-wave excitation and surface-enhanced Raman scattering (SERS), we have carried out experimental studies on SERS characteristics of the 2×2 fused fiber coupler coated with Ag colloid particles. By stretching a pair of fused single-mode fibers with coating Ag colloid on its surface, the formed component can work as the surface-active substrate to perform Raman enhancement. With increase of the taper length, fiber core diameters decrease and less energy are bounded in the fiber. This enables stronger evanescent-wave to leak outward and become a Raman exciting source. In the experiments, the Raman spectra of R6G solutions has been detected at the coupling zone. The minimum detected concentration is 10^-8 mol/L.