Design And Fabrication Of Silicon Photon Mode Size Converter

The wedge mode size converter can adjust the size of the spot adiabatically to make it matched and coupled to the optical fiber.It has the advantages of intuitive shape,simple packaging,high coupling efficiency,and easy integration.With the emergence and development of optical communications,optical storage,optical switches,artificial intelligence and other fields,silicon photonic mode spot converters have gradually become practical,bringing us a lot of convenience.At present,gray mask,electron beam gray exposure,shadow coating,shadow etching,wet etching and other methods are widely used in the manufacturing process of wedge-shaped pattern converter at home and abroad.The process is complex,the manufacturing cycle is long,the cost is high,the repeatability is low and it is difficult to mass produce,so it is difficult to move from the laboratory to the specific application.Therefore,in this paper,the new preparation method of the wedge mode size converter is studied,and the mode transformation in the large end face wedge mode size converter is studied.The main research contents are as follows:(1)Based on the analysis of the basic theory of optical waveguide and the coupling loss of optical waveguide when it is connected with optical fiber.Optimizing wedge parameters through computational design.When the incident light wavelength is 1550 nm,the end face size of the mode spot converter is at least 2 μm×2 μm,and the wedge length is greater than 18 μm.It can achieve the best coupling efficiency,which greatly reduces the coupling loss when it is docked with the optical fiber.(2)The designed wedge mode size converter was prepared.Through the ultraviolet lithography and deep silicon etching,a 1μm wide and 0.22 μm high side wall is used to make a coupled optical waveguide.The bonding parameters were optimized according to the direct bonding theory,and bonds and interfaces with voids less than 10 nm were obtained.Through the new method of step-by-step re-exposure system combined with high temperature thermal reflow,optimize the exposure time to 20 ms/times,and reflow at 160℃ for 1 min,a wedgeshaped pattern mode size converter with a length of 21 μm and an end surface size of about 3μm×3.5μm was prepared on the bonding sheet.The coupling loss was approximately-0.3d B,and the device coupling loss was-3d B.(3)The mode conversion of large end wedge converter is studied.Through the study of the mode coupling theory of optical waveguide,the mode transformation of the converter in which the light incident on the large end face is simulated by FDTD software,It is obtained that the wedge length is 100 μm and 150 μm,the width is 5μm,the height is 1 μm,the waveguide width is 1 μm,and the height is 0.22 μm.There is a mode change in the wedge height between 0.1 and 0.3 μm.The light spot is converted from one to two.The simulation results show that the coupling efficiency is above 98% and 93%,respectively.The coupling efficiency of the optical waveguide and the wedge is simulated,and the coupling efficiency is reduced from 92% to 75% when the waveguide misalignment error is increased from 0.5 μm to 1 μm.