Fig. 1. Schematic of femtosecond laser processing

Fig. 2. Microcavity microscopy in multimode fiber. (a) Front view; (b) side view

Fig. 3. Schematic of sensor structure

Fig. 4. Light path diagram of sensor

Fig. 5. Transmittance spectrum of sensor

Fig. 6. Spatial spectrum of sensor

Fig. 7. Schematic of temperature experimental device

Fig. 8. Transmittance spectra of sensors at different temperatures

Fig. 9. Linear fitting diagram of high temperature experiment

Fig. 10. Schematic of refractive index experimental device

Fig. 11. Transmittance spectra of sensor in different refractive indexes

Fig. 12. Linear fitting diagram of refractive index experiment