A unique all-fiber interferometric sensor was proposed and successfully demonstrated efficient low-refractiveindex liquid sensing in the range from 1.33 to 1.37, which is compatible with those of bio-liquids. A special silica coreless optical fiber with an open V-groove was used as an optical sensing medium, which provided a high sensitivity for a minute liquid volume in the nanoliter scale. The V-groove fiber (VGF) was serially concatenated between two single-mode fibers (SMFs). The LP01 mode guided along the input SMF excited the higherorder modes in the VGF to generate multimode interference, whose spectrum was transmitted through the output SMF. A single liquid droplet with volume of ~80 nanoliters wet the entire hydrophilic surface of the VGF, and the transmission spectra shifted corresponding to its refractive index in a very linear manner. The sensor also showed a negligible temperature cross-sensitivity in the range 25°C-75°C, which overlaps with the biological temperature window such that the sensitivity of 159.696 nm per refractive index unit (nm/RIU) remained independent of the temperature variation. Modal properties of VGF were thoroughly analyzed numerically, and detailed processes for the sensor fabrication and sensing experiments were reported.
Bibliographical noteFunding Information:
Funding. LG Display under LG Display-Yonsei University Incubation Program (2018-11-1448); National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2019R1A2C2011293); National Natural Science Foundation of China (NSFC) (61805054); Fundamental Research Funds for the Central Universities of China (3072019CFJ2501).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics