Multifunctional optoelectronic device based on liquid crystal selectively filled flat-plate photonic crystal fiber

To reduce the saturation voltage of fiber filter and improve the sensitivity of voltage sensing, we propose and numerically demonstrate a multifunctional optoelectronic device with a flat-plate photonic crystal fiber structure in this paper. One of the air holes is selectively filled with liquid crystal, and the upper and lower planes of the fiber are plated with gold films to form electrodes. Based on the applied voltage, the coupling wavelength of the core fundamental mode and filling mode is adjusted. This structure can realize the functions of tunable filtering and external voltage sensing. In addition, the metal film is close enough to the fiber core to enable coupling between the core waveguide mode and the surface plasmon resonance mode. Thus, the external RI can be measured. The measurements of the voltage and refractive index of the device are independent of each other, thus realizing a simultaneous measurement of the two parameters. We used the finite element method to investigate its photoelectric characteristics systematically. When the thickness of the plate fiber is 18 µm, as a fiber filter, the applied saturation voltage decreases from 2900 V (photonic crystal fiber with a conventional structure) to 650 V, and the threshold voltage decreases from 45 to 8 V. When used as a voltage sensor, the voltage sensitivity is improved from 0.025 to 0.117 nm/V. As a dual-parameter sensor for simultaneously measuring the voltage and RI, the RI sensitivity is 2700 nm/RIU. Evidently, the superior performance of the proposed structure renders it a high application value in the fields of optical fiber sensing and communication. © 2021 Elsevier GmbH