A NOVEL ALL-FIBER ELECTRIC FIELD SENSOR BASED ON TAPERED FIBER-SLAB WAVEGUIDE COUPLER

□ A novel optical electric field sensor based on evanescent coupling between a tapered fiber and a slab waveguide is proposed and demonstrated. Light in a tapered fiber evanescently couples into the slab waveguide and forms a wavelength resonant spectrum. A slice of a LiNbO₃ crystal was used as the slab waveguide. External electric fields may change the refractive index of the crystal and thus make the resonant wavelengths shift. Therefore, an optical electric field sensor was obtained by measuring the wavelength shift caused by an external electric field. The principles and design of the proposed sensor are reported. The performance of the proposed sensor are demonstrated experimentally by detecting sinusoidal fields with 50 Hz and pulsed electric fields with a rise time of 1.2µs. The results show that the minimal detectable field was approximately 150 V/cm with a signal-to-noise ratio of three.