Simultaneous measurement of relative humidity and temperature using a microfiber coupler coated with molybdenum disulfide nanosheets

The simultaneous measurement of relative humidity (RH) and temperature with an optical fiber sensor is proposed based on a microfiber coupler (MFC) coated with a single layer of molybdenum disulfide (MoS2) nanosheets. The MFC is fabricated using flame heating technology and has a waist diameter of approximately 6 mu m and a waist length of approximately 3 mm. As the RH increases, the effective refractive index of MoS2 varies as a result of electric charge transfer, the spectrum dip shifts toward longer wavelengths, and the transmission intensity of the spectrum decreases. As the temperature increases, the refractive index of the cladding of the fiber in the MFC waist region increases due to the thermo-optic effect, the spectrum dip shifts toward shorter wavelengths, and the transmission intensity of the spectrum decreases. The experimental results show that the RH sensitivities are 115.3 pmP%RH and -0.058 dB/%RH in the range of 54.0 - 93.2%RH. The temperature sensitivities are -104.8 pm/degrees C and -0.042 dB/degrees C in the range of 30 - 90 degrees C. The proposed sensor is expected to be used for simultaneous measurement of RH and temperature in the field of biochemical analysis. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement