Fig. 1. Experimental device for SERS spectrum detection of micro-cavity fiber probe

Fig. 2. The change of micro-cavity length with etching time
(a): Microscope image; (b): Quantitative result figure

Fig. 3. Experimental results of the mixed solution to find the best enhancement effect
(a): Raman spectra of nano silver sol and R6G solutions mixed with different mix orders and ratios;(b): Raman intensity of different mixed solutions at Raman shift of 1 510 cm^-1

Fig. 4. Micro-cavity fiber SERS experiment results
(a): SERS results of optical fiber micro-cavity with different etching time;(b): Raman intensity of fiber micro-cavity with different etching time at Raman shift of 1 510 cm^-1

Fig. 5. The active fiber tip modified with silver nanoparticles by magnetron sputtering method modified with silver nanoparticles by magnetron sputtering method

Fig. 6. Probe performance results
(a): Sensitivity test; (b): Linear relationship between logI and logC centered at 1 362 cm^-1 in Raman spectrum

Fig. 7. Experimental results
(a): Reproducibility test of fiber SERS probe; (b): Raman spectra of fiber probe and bare fiber