Abstract

An optical fiber ultrashort polymer micro-nano waveguide Bragg grating (PMWG) for contact liquid temperature sensor was fabricated on the single-mode fiber tip by the femtosecond laser induced two-photon polymerization. This structure is composed of a conical waveguide, a micro-nano waveguide Bragg gating and a pair of tripods. The overall length of the structure is about 160 μm and the cross-sectional dimension of micro-nano waveguide is only 1.6 * 1.5 μm. The length of polymer micro-nano waveguide Bragg grating is less than 125 μm, which is about one fiftieth of the traditional FBG. The micro-nano waveguide grating was placed in deionized water. The surrounding liquid acts as the cladding of the micro-nano waveguide grating. The direct contact of the grating structure with the external liquid will result in faster and more sensitive liquid temperature response. In the liquid temperature corresponding experiment, the sensitivity of the micro-nano waveguide grating is up to 0.3385 nm/°C with deionized water temperature changing from 27.7 °C to 49.2 °C. It has a good application prospect in the field of optical fiber biochemical micro-nano detection, microfluidics, etc.