A fiber-optic violet sensor by using the surface grating formed by a photosensitive hybrid liquid crystal film on side-polished fiber

Abstract

A fiber-optic violet sensor is demonstrated by using the surface grating formed by a photosensitive liquid crystal (LC) hybrid film on the flat area of side-polished fiber (SPF). The surface grating is constructed through a periodic intensity illuminating the hybrid LC film, where the periodic intensity is created by a phase mask through which the violet light passes. Experiment shows that a loss peak appears in the transmission spectrum between 1520 and 1620 nm, and this loss peak shifts toward shorter wavelength as the 405 nm light power increases. The wavelength shift of the peak shows very good linearity with the irradiation power between 30 and 80 mW cm−2. The very high sensitivity of the light power sensor is measured to be 1.154 nm (mW cm−2)−1, which implies that the minimum change of power intensity that can be detected is 0.866 µW cm−2 for this sensor under the limited wavelength resolution of 0.001 nm of the optical spectrum analyzer. For UV light, much higher sensitivity will be further obtained, as the LC hybrid is more sensitive to UV light than to violet light.

Sensing Characteristics of Side-Polished Fiber Based on the Alterations in Helical Structure of Thermo-Sensitive Cholesteric Liquid Crystals

“…Several studies have [18,19] proposed that azobenzene polymer can be introduced to the nematic liquid crystal and coated on the polished surface of SPF, through which an optically controllable SPF attenuator is made based on the liquid crystals. However, Yu et al [20,21] coated the mixed liquid crystals onto the side-polished surface of SPF and managed to fabricate an optically powered fiber optic sensor. Tang et al [22] successfully fabricated optical fiber-based volatile organic compound gas sensors by coating CLCs onto the polished surface of SPFs.…”

Response Characterization of a Fiber Optic Sensor Array with Dye-Coated Planar Waveguide for Detection of Volatile Organic Compounds

“…Recently, side-polished optical-fiber sensors have been shown to be good candidates for monitoring environmental changes because they not only have mechanical stability, but also sensitivity control by changing the planar waveguide materials [ 12 – 17 ].…”

Hybrid optical fiber add-drop filter based on wavelength dependent light coupling between micro/nano fiber ring and side-polished fiber

“…Therefore, guided light mode field can interact with the optical medium on the polished area, making it possible to coupling light with a MNOF disposed there. Benefitting from this advantage, various optical fiber devices, including optically reconfigurable surface grating fiber 22 , optically controllable fiber-optic rotator 23 , and various optical fiber sensors 24 25 26 , have already been demonstrated. Secondly, the polished area provides a platform to mount and fix a MNOF with relative ease, thus enabling possible integration of a MNOF-based device with a standard optical fiber.…”