Light-Controlled Asymmetric Dual-S-Taper Fiber Interferometer Integrated With Ethyl Orange Solution Under 473 nm Laser Illumination

An azobenzene (azo)-integrated asymmetric dual-S-taper fiber interferometer based on concatenated single-mode fiber S-tapers is proposed and fabricated. As the fiber interferometer is immersed into the ethyl orange (EO) solution, due to the photo-isomerization effect of azo materials, azo molecules would experience conformal change when 473 nm laser illumination is applied, resulting in the variation of ambient surrounding refractive index. Transmission spectra of the proposed dual-S-taper structure exhibit stable and regular wavelength shift under different illumination light intensities or EO weight percentages of EO solutions. An optimal EO weight percentage of 0.1 wt% was experimentally acquired with wavelength sensitivity reaching −27.6 pm/mW for a laser power range of 0 mW to 195 mW. Furthermore, repeated laser power increasing and decreasing experiments and the control experiment under the distilled water environment proves our proposed fiber interferometer with highly reversible and stable light-sensitive wavelength responses, making it a good candidate for light intensity sensing and light-controlled wavelength-tuning applications in future all-optical networking systems.