Fiber optic DC electric field sensor based on electrically tunable liquid crystals

Abstract Two fiber optic direct current (DC) electric field sensors are proposed based on electrically tunable liquid crystal (LC) is proposed. The two sensors have the transmissive and reflective structure, respectively. The multimode fiber is connected to the LC device, enabling the measurement of the transmittance and reflective interferometric spectra. The variation of the applied electric field can cause the change in the effective refractive index of the LC, and the intensity or wavelength of light passing through the LC device can be continuously tuned when the applied electric field exceeds a threshold value. In the electric field range of 280–520 V/mm, with the increase of the electric field intensity, the transmittance of the sensor decreases, the linear sensitivity is 0.40549 %/(V/mm) with the detection limit (LOD) of 0.20028 V/mm. For the sensor with the reflective structure, the blue shift occurs with the increase of electric field intensity, and the linear sensitivity of 0.0474 nm/(V/mm) with the LOD of 0.12152 V/mm. In addition, the sensors have the advantages of good repeatability, low cost, high sensitivity, etc., and have potential applications in the electric field sensing and photoelectric switches.