We have fabricated aminopropyltriethoxysilane (APTES)-functionalized nanoporous polymeric gratings by combining holographic interference patterning and APTES-functionalization of the pre-polymer syrup. The APTES facilitates the immobilization of biomolecules onto the polymeric grating surfaces. The successful detection of multiple biomolecules (biotin, steptavidin, biotinylated anti-rabbit IgG, and rabbit-IgG) indicates that the functionalized nanoporous polymeric gratings can act as biosensing platforms which are label-free, inexpensive, and applicable as high-throughput assays.

This paper demonstrates light-induced tuning of the optical spectrum by a microfiber-knot resonator overlaid with a photoresponsive liquid crystal (LC) mixture containing photosensitive diluents (non-mesogenic azobenzene molecules), a chiral dopant and a nematic LC. The high-quality resonator is made by drawing a single mode fiber to a micro-size diameter and causing the microfiber to self-twist into a knot. A thin layer of a photosensitive mixture was placed on the overlap (knot) area and gentle heating was used to obtain a uniform thin film which coated the fiber’s surface. Upon irradiation with UV light, noticeable changes to the peak resonance wavelengths were observed which we associate with a local change in the refractive index (RI) in the fiber’s tapering area. Repeatable and reversible spectral shifting (0.15 nm) of the resonance wavelength is demonstrated by irradiation with 50 mW/cm² UV light.

This study presents an optically controllable fiber-optic attenuator consisting of side-polished fiber (SPF) with a photoresponsive liquid crystal (LC) overlay operating in the telecommunication wavelength. Attenuation is controlled by a photochemical-induced phase transition of photoresponsive LC, which modulates the evanescent field leaked from the polished area. Before optical field illumination, the photoresponsive LCs are in the light-scattering state and attenuation is high. During photoirradiation, the formation of cis-azobenzene LC disrupts the nematic host and generates a light-transparent state in which the optical loss of the SPF attenuator decreases. The photoinduced tuning range is 15 dB at an environmental temperature of 45 °C, and a repeatable and reversible tuning is observed with a response time of less than 5 s. The proposed all-optical controllable attenuator has potential use as an optical signal modulator in an all-fiber telecommunication system.