Miniature -shaped polymer fiber tip for simultaneous measurement of the liquid refractive index and temperature with high sensitivities

A miniature fiber sensor tip with both high refractive index (RI) and temperature sensitivities was proposed for measuring the temperature and liquid RI simultaneously. A two-photon polymerization technique was used to fabricate a -shaped polymer micro-structure on the end-face of an optical fiber. A three-wave Fabry-Pérot interferometer was formed. The size of the proposed FPI can be precisely controlled and the total height is less than 30 μm. Temperature and RI variations can be detected simultaneously using the sensitivity matrix method. The sensor tip can be used in harsh environments, as cross-linking SU-8 has moderate acid and alkali resistance and good mechanical strength.