Research On Electro-optic Modulator Based On Lithium Niobate Thin Film

Lithium niobate modulator is widely used in current communication network because of its advantages such as wide band adjustable,high extinction ratio,mature technology and easy to mass production.However,with the development and research of indium phosphide and silicon materials,the modulator of new materials impacts the market of lithium niobate modulator,and the existing lithium niobate modulator is facing the crisis of being replaced gradually.Lithium niobate modulator to maintain the existing market and even further development,there must be technological innovation.The research of new lithium niobate thin film materials brings hope to the market of lithium niobate materials.The new lithium niobate thin film modulator has the advantages of small size and easy integration while maintaining the excellent electro-optic characteristics of lithium niobate,which fits the development direction of the next generation optical communication network and has important research value.In this thesis,a lithium niobate thin film modulator is designed.The optical part adopts a symmetrical X tangential light push-pull MZI modulator structure and a lithographic etching ridge waveguide on lithium niobate thin film as a waveguide manufacturing technology.The main research contents are as follows:(1)Design and manufacturing of the center wavelength of 1550 nm based on Y branch structure of lithium niobate thin film waveguide,2x2 MMI coupler structure and the structure of grating coupler,the Y branch waveguide structure and 2x2 MMI coupler structure are all the work points as MZI modulator structure design,through the experiment contrast,proved more close to 1:1 ratio Y branch waveguide structure,more stable performance,the Y branch waveguide as the structure of lithium niobate thin film modulator work points.The design of thin-film waveguide not only greatly reduces the volume of modulator,but also reduces the driving voltage required by modulation,which not only ensures the modulation performance,but also reduces the power consumption and volume of the device,which is conducive to the development of integrated communication system.(2)According to design the structural parameters of the waveguide structure of lithium niobate thin film electrode of the modulator,with coplanar waveguide traveling wave electrode structure design,based on the electrode of titanium and alloy material,and according to the dc voltage modulator,modulation bandwidth indicators such as optimization,through the optimized modulation performance and comparison of similar modulator,proved this topic design of lithium niobate thin film modulator has application value.(3)A new end-face coupling structure is designed,in which trident structure and rasterlike conical structure are used to expand the coupling mode field of the thin-film waveguide and reduce the coupling loss.Due to the small thickness of the thin film,the lithium niobate thin film waveguide structure has the problem of mismatching with the optical fiber mode field during the end coupling and large coupling loss.This new type of end-face coupling structure will reduce the insertion loss of lithium niobate thin film modulator and improve the modulation efficiency.