| Fiber optic polarizers are important optical passive components for generating and detecting polarized light.They are key components of high-capacity coherent communication,high-sensitivity fiber optic sensing systems and precision fiber optic metrology systems.Designing and developing a new type of fiber optic polarizer with high extinction ratio,low loss and high integration has an important role in promoting the rapid development of polarization-related systems such as optical communication and fiber optic gyroscope.The continuous improvement of graphene material preparation technology and its excellent physical properties provide a new type of material for fiber polarizers.In this paper,a novel fiber-optic polarizer based on graphene material was studied by using the tunable characteristics of graphene.The main work is summarized as follows:Firstly,MatLab software was used to program the formula of conductivity and dielectric constant of graphene,and the electrical properties of graphene materials were analyzed to provide a theoretical basis for the application of graphene materials in polarizers.The transmission characteristics and mode theory of optical waveguides are analyzed from the wave theory.The solution process based on full vector finite element analysis method and the basic ideas of this method in fiber analysis are introduced.Then,a double D-shaped hole fiber is proposed.The simulation of the double D-shaped hole fiber is carried out by using the finite element method based COMSOL Multiphysics software.The mode characteristics,birefringence characteristics and evanescent field characteristics of the fiber are analyzed.The influence of incident wavelength and fiber parameters on fiber birefringence and its evanescent field is analyzed.It can be concluded from the simulation results that when the distance between core and D-shaped hole is 0.1?m,the birefringence of the fiber can reach 3.8×10-4,The energy percentage of the evanescent field in the holes can reach 1.2%,which provides a theoretical basis for the next step of laying graphene in the D-shaped hole to make the fiber polarizer.Finally,the polarization characteristics of the fiber are simulated when the single-layer graphene material is coated in the D-shaped hole.The effects of incident wavelength,fiber parameters and graphene parameters on the transmission characteristics of the fiber are mainly analyzed.From the simulation results,when the fiber length is 2.5 mm,the extinction ratio can reach 24.1 dB for the TM-pass polarizer,and the extinction ratio can reach 42.5 dB for the TE-pass polarizer,and the parameters of the graphene material can be adjusted.At a center wavelength of 1.31?m and 1.55?m,a double bandwidth effect can be achieved.The fiber polarizer proposed in this paper take advantage of an elliptical core to strengthen the working area of graphene and the core.And on the other hand,by coating graphene in the planar surface of upper and lower D-shaped holes,the intensity of action of light and graphene is enhanced.Compared with the previous proposed fiber polarizers the extinction ratio is greatly improved,and the fiber length is also closer to miniaturization.This high extinction ratio,low loss,miniaturization,tunable fiber polarizer will have a good application prospect in polarization-related systems. |
PDF Full Text Request