Research On The Photonic Devices Of Functional Materials Filling Microstructured Optical Fibers

The functional materials infilling microstructured optical fibers combining the physical effects of functional materials with the fiber micro/nano structure, show advantages of flexibility in design, tunability under external fields, easy to integration and all in fiber, providing a promising platform for novel fiber photonic devices. In this paper, we investigate the refractive index property of functional materials, such as liquid crystal, magnetic fluid, gold and aluminum. Modes coupling theory of the designed functional materials infilling microstructured optical fibers are studied based on optimal design of air holes and infilling position. The performances of the designed photonic devices are characterized.First, functional materials with refractive index influenced by external fields are designed to be infiltrated into one cladding air hole in silica microstructured optical fibers. The influence of external fields on coupling between core modes and defect modes are studied. The simulation results show that the coupling is complete when the functional materials infiltrated air hole is adjacent to fiber core. The coupling intensity is strong while the spectrum of confinement loss is broad. The coupling is incomplete while the functional materials infiltrated air hole is far away from the fiber core. The coupling intensity is weak, but the spectrum of confinement loss is narrow. The refractive index of functional materials can be adjusted by external fields. The coupling between core modes and defect modes can be modulated by external fields and therefore fiber sensor can be realized.Second, one air hole between two fiber cores in dual-core silica microstructured optical fibers is designed to be infiltrated with nematic liquid crystal. The polarization filtering properties of the designed fibers are influenced by the refractive index of liquid crystal under electrical field and temperature. The light transferring in fiber core is still refractive index guiding due to only one air hole between two fiber cores infilltrated with liquid crystal of high refractive index. Broad bandwidth polarization splitter is obtained. The designed fibers show good polarization splitting characteristics as fabrication tolerance reaching to 1%.Third, the metal material of gold is designed to infiltrate in single-core, dual-core and three-core microstructured optical fibers. The influence of surface plasmon resonance on polarization filtering and splitting is investigated. The polarization filter based on single core microstructured optical fibers with ultrabroad bandwidth is obtained due to cascaded resonances between core modes and surface plasmon polariton modes. Based on the modulation of surface plasmon resonance on refractive indices of supermodes in dual-core and three-core microstructured optical fibers, polarization splitters with excellent properties of high extinction ratio, broad bandwidth, low insert loss, short coupling length are achieved.Finally, the metal material of aluminum with low melting temperature is designed to be infiltrated in microstructured optical fibers. The influence of surface plasmon resonance on polarization filter and sensing are investigated. Polarization filter with ultrashort fiber length and ultrabroad bandwidth is achieved based on large difference of surface plasmon resonance between core modes and surface plasmon resonance in two orthogonal directions. Due to the modulation of refractive index of analyte on coupling intensity between core modes and surface plasmon polariton modes, an intensity-type refractive index sensor with high sensitivity and broad measuring range is obtained.