The Research On Transmission Characteristics Of Micro-nano Optical Waveguide And Its Application

Because of its nanoscale structure and high located ability to light field,low loss and small quality,nano-optical waveguide played a very important role in optical communication,optical sensing,military,medical devices and nonlinear optics.With the appearance of different types of micro-nano waveguides,the functional and controllable characteristics of optical devices have become one of the hottest topics for researchers in the field of micro-nano optical field.Based on the functional optoelectronic materials,such as the materials with the characteristics of electro-optic,acousto-optic,and piezoelectric materials,by designing its structures properly,we can realize some functions that are difficult to achieve with conventional devices,such as the characteristics of large waveguide dispersion,large nonlinear coefficient,and abnormal transmission.Our study mainly focuses on how to realize the controllable waveguide characteristics and conducts research work on the transmission characteristics and applications of micro-nano optical waveguides.The research contents are mainly divided into the following aspects:(1)Dispersion characteristics and its regulation ability of lithium niobate micro-nano waveguide were analyzed numerically,and the influences of waveguide structure parameters and external field conditions on its dispersion characteristics were obtained.A three layer waveguide structure is designed with intermediate LiNbO3 cladding.First,we derived the eigen equations of the micro-nano waveguide we designed theoretically,then,we discussed the dispersion characteristics at the visible wavelength 633 nm and the optical fiber communication wavelength 1550 nm.By changing the diameter of the inner core of the fiber or changing the thickness of the lithium niobate film,we can change the the value of dispersion significantly.The most notable point is that,by using the electro-optical characteristics of lithium niobate material,the dispersion characteristics of the optical fiber can be effectively controlled by applying an external voltage.(2)The broadband group velocity dispersion characteristics of lithium niobate micro-nano waveguides were studied numerically,and the regulation of dispersion characteristics in the mid-infrared wavelength region was obtained.A three-layer waveguide structure with a silicon core and a lithium niobate film cladding was designed.We found that lithium niobate micro-nano fibers have large dispersion values of group velocity dispersion and can be used as broadband dispersion compensators in the mid-infrared wavelength region.We mainly focused on the group velocity dispersion characteristics at the wavelengths of 3 ?m,4 ?m,and 5 ?m,and discussed the influence of changes in the diameter of the silicon core and changes in the thickness of the lithium niobate cladding on the group velocity dispersion.At the same time,we discussed the effect of the applied electric field intensity on the group velocity dispersion of our designed fiber structure.The numerical calculation results showed that,on one hand,the group velocity dispersion of our design can be adjusted by selecting different structure sizes,on the other hand,the group velocity dispersion can also be adjusted by changing the optical parameters of the material.(3)We numerical studied the transmission characteristics of the hollow micro-nano optical fiber waveguide with lithium niobate material,and obtained its regulation in the generation of super-continuous light.We designed a type of lithium niobate hollow core nanofiber with lithium niobate tube,and its mode field characteristics,energy density,waveguide dispersion characteristics,mode field diameter and nonlinear parameters were numerically analyzed.The numerical results showed that the lithium niobate nanowire with hollow core has strong optical field in the air-core layer,which can be used to enhance the interaction between light and matter.In addition,on the outer surface of the lithium niobate hollow nanowire,the evanescent wave can be transmitted and used to achieve optical field coupling with other components.Moreover,lithium niobate hollow core micro-nanofibers have small mode field diameters and large nonlinear parameters,which are very important for us to design photonic devices in the field of nonlinear optics.(4)The anomalous reflection of light was realized for the first time based on the effect of plasma tunneling,and the influence of structural parameters on its abnormal reflection behavior was obtained.Based on the metal-medium-metal(MIM)structure,the tunnel junction composed of MIM was studied.We deduced the relationship between tunnel current density,tunnel conductivity and tunnel damping constant of the structure.We also discussed the influences of particle mass and barrier height of the junction on tunnel current density,tunnel conductivity and tunnel damping constant.Using the obtained range of damping constants,we conduct voltage regulation on the hypersurface composed of two cascaded periodic MIM structures we designed.When a beam of polarized electromagnetic waves in the x direction with wavelenght at 3 ?m was Irradiated on the metasurface,we can obtain a phase gradient with constant,and this phase gradient constant can be adjusted.By changing the voltage value we applied on each MIM waveguide component,the proposed MIM metasurface with plasmonic tunneling effect can achieve the adjustment of the abnormal reflection angle in the range of 0-15 degrees.