Research On Lithium Niobate Waveguide Grating And Application Based On Photorefractive

The waveguide devices,as a very important part of optical integrated devices,have attracted extensive attention in the era of optical communication network,in which photons take places of electrons as alternative information carrier.Among them,the waveguide gratings have broken through the limitations of the traditional fiber gratings in structure and material selection.Meanwhile,it is easy to integrate and mass production,and easy to be tuned in real time with electronic controlling,the waveguide grating has become a hot topic.Lithium niobate?Li NbO₃?crystal is one of the most promising substrate materials for various waveguide grating substrate materials due to its excellent optical properties.There are different types of waveguide gratings can be fabricated by using LiNbO₃ crystal as substrate material.Among these gratings,the photorefractive gratings are simple in fabrication,small in size,low in cost and easy to erase,so that photorefractive gratings have a good application prospect in integrated optics.In this thesis,x-tangential LiNbO₃ crystal is used as the substrate material,single-mode titanium diffused optical waveguides are fabricated.And the photorefractive long period grating and Bragg grating were fabricated.At the same time,propose the application design of long period waveguide grating.The details are as follows:Firstly,analyze the theory of long period waveguide grating,then analyze the influence of the parameters on the transmission spectrum by simulation and the parameter of the long period waveguide grating is determined.Finally produce the photorefractive long-period gratings with the method of amplitude mask,resonant wavelength is 1530 nm,and the contrast is 4.5dB.The feasibility of using photorefractive effect to fabricate grating is proved.Secondly,analyze the theory of photorefractive Bragg waveguide grating produced by double-beam interference.Then,the influence of parameters on the reflection spectrum of Bragg grating is analyzed by simulation and the parameters of Bragg grating is determined.Finally,the experiment of Bragg grating was carried out by using the method of two-beam interference.And the possible causes of experimental measurement are analyzed.Thirdly,proposed the application design of the long-period waveguide grating,long-period waveguide grating tunable coupler.Firstly,the structure and principle of the tunable coupler are introduced.Then effects of the parameters on the coupler spectrum and the tunable performance of the coupler are analyzed.Finally,the design of the specific parameters is given and the performance of the coupler is analyzed.The tuning rate can reach nanosecond level in theory.