Sensitivity enhancement of ultraviolet sensors utilizing 80-μm-diameter fiber Bragg gratings coated with azobenzene polymer

• Published in: Sensors and actuators. A. Physical. Vol. 368; p. 115126
• Main Authors: Kang, Hanmam, Ko, Youngmin, Moon, Jongju, Seo, Jungmin, Ahn, Tae-Jung
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2024
• Subjects: Fiber Bragg grating; Fiber optic sensors; Ultraviolet light measurement; Ultraviolet light measurement; Fiber Bragg grating; Fiber optic sensors
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2024.115126

This study presents an advanced fiber Bragg grating (FBG) ultraviolet (UV) sensor utilizing an 80-μm single mode fiber (SMF) with a UV-reactive azobenzene polymer coating. We circumvent the conventional hazardous hydrofluoric acid etching process for FBG diameter reduction, yielding low reproducibility and compromised fiber robustness. Instead, our method employs a thinner SMF to enhance strain sensitivity while maintaining structural integrity. We examined the impact of azobenzene coating thickness on UV sensitivity, comparing 250 µm and 900 µm coatings. The results demonstrated that the 900 µm coating significantly increased the UV responsiveness without compromising the reversibility of the sensor’s reaction to UV exposure. In addition, the FBG’s central wavelength shift exhibited a linear response to UV intensity changes, with the 900-μm coating demonstrating a 3.5-fold increase in responsiveness over the 250-μm coating. This innovation enables the development of highly sensitive and durable UV sensors, offering a safer and more effective alternative to conventional FBG fabrication techniques. [Display omitted] •Introduced azobenzene polymer coating on 80-μm-diameter Fiber Bragg Gratings, enhancing the UV sensitivity of the sensors.•900-μm azobenzene coating on FBGs results in a 3.5-fold increase in UV responsiveness compared to a 250-μm coating.•A safer and more reproducible method for sensor fabrication for FBG diameter reduction is suggested.•The wavelength shift of the FBG exhibits a linear relationship with UV light for reliable UV sensing applications.