Research On The Design And Performance Of Photonic Devices Based On Microstructuerd Optical Fibers Filled With Materials

Microstructured optical fibers(MOFs)and the photonic devices are hot topics among the research of optoelectronic fields,and the flexibility of their geometric structures makes the MOFs more advantageous over conventional fibers,especially for the control of dispersion,confinement loss,polarization,nonlinearity as well as the modes.It paves a novel way for the combination of the functional materials and the MOFs,which is a candidate for the improvement of the property and the extension of their application.In this paper,the characteristics of the MOFs with various structures are theoretically modeled utilizing the finite element method(FEM)on the basis of the optical waveguide principle,the coupled mode theory(CMT)and the phenomenon of surface plasmon resonance(SPR),and the superior performance of the infiltrated MOFs-based polarization splitters,polarization filters and optical sensors are designed and numerically analyzed.We also propose a sensing detection system based on a liquid-filled negative curvature antiresonant reflection(ARR)hollow core MOF integrated with the Raman scattering effect(RSE).The Raman spectra of a series of low-concentration ethanol solutions are measured and a good linearity and a low limit of detection(LOD)can be obtained in theory and experiment.The main points are as follows:First,two types of dual-core MOFs polarization splitters are designed based on the CMT.The influence of the geometric parameters on the effective refractive index,the birefringence and the confinement loss are modeled through the FEM.We calculate the coupling lengths and extinction ratio of two orthometric polarization states of the core mode,and it is found that the two states can be separated into two cores as their coupling length ratio satisfies the condition of 2 or 1/2.Two polarization splitters with high extinction ratios at the communication wavelength of 1.55 μm are realized.Second,three kinds of single-core MOFs polarization filters based on the effect of SPR are proposed.SPR can be excited by selectively gold-filled or gold-coated on the MOF.The effective refractive index and the confinement losses of the core modes and the surface plasmon modes are simulated by the FEM,and the phase-matching points of the effective refractive index and the resonant points of the loss curves are analyzed.In particular,we obtain a 20 nm narrow-band single polarization filter based on a gold-filled MOF operating in the two communication wavelengths of 1.31 μm and 1.55 μm and an ultra-broadband single polarization filter based on a gold-coated MOF with a low-loss bandwidth of 1310 nm;A wavelength-tunable polarization filter with a glycerin-filled and gold-coated MOF is designed,and the variation of the temperature can be also monitored according to the shift of resonant peaks due to the temperature-sensitive feature of the glycerin,illustrating the possibility of the incorporation of polarization filters and temperature sensors.Third,on the basis of the polarization character of the glycerin-filled and gold-coated MOF,the compatibility of filter and temperature sensor with one fiber is first proposed.And we obtain a temperature sensor by monitoring the shift of the resonant peaks on temperatures at shorter wavelengths in the two polarization states.We then design a gold-coated sidepolished MOF,the effects of the side-polished depth,the gold layer thickness,the geometric parameters as well as the refractive index of the analytes to be detected on the confinement losses are simulated by the FEM.The highest wavelength sensitivity and amplitude sensitivity are obtained.The introduction of the side-polished surface not only provides a simple stage for gold coating and analytes detection,but also it can enhance the intensity of the SPR.Finally,a low-concentration specific sensing system based on a liquid-filled negative curvature hollow core MOF is designed.The transmission spectra of the MOF before and after filling are modeled by the FEM,and it demonstrates that the mechanism of ARR is advantageous for the simple structure,the low loss and the broad transmission band covering from the visible to near infrared region.We make full use of the low Raman background interference provided by the hollow core MOF and the "fingerprint" Raman scattering spectra of analytes to investigate the sensing ability of the negative curvature MOF.The Raman sensing detection system is set up in experiment with the aid of the backward collection geometry.The specialized Raman spectra of air,methanol,ethanol,isopropanol and the low-concentration ethanol solutions are analyzed.The quantitative and qualitative detection capability of our system is verified in theory and experiment,and the LOD as low as 0.075 vol.%is achieved,which can be widely used in the applications of high sensitive and portable optical sensors.