Lateral Leakage Loss Analysis And Device Design Of Shallow-etched Rib Waveguide On SOI With Arc Cross-section

The development of integrated optics needs basic research in bottom devices,and rib waveguides on silicon-on-insulator?SOI?are widely used in integrated optics.This thesis put forward a kind of shallowly-etched rib waveguide on SOI with arc cross-section after the study of related literatures,and then a directional coupler using this waveguide is designed.The theory and simulation of shallowly-etched rib waveguides on SOI with arc cross-section will provide useful guidance for the fabrication of waveguides and devices.In order to further investigate the lateral leakage loss behavior of shallowly-etched rib waveguides on SOI,a kind of shallowly-etched rib waveguide with arc cross-section is proposed and analyzed.A periodical loss model and a formula of loss period of this waveguide are obtained by the interference theory,and then phenomena of periodic variation of lateral leakage loss and shift of the maximum loss point for transverse magnetic fundamental-like mode?TM₀-like mode?are observed through a finite element method simulation in frequency domain with perfectly-matched layer conditions.The period in s imulation results are highly consistent with theoretical calculation,and the average relative error is only 0.56%.In addition,it is found that we can adjust TM₀-like mode loss from maximum to minimum by changing the cross-section of rib waveguides with some trench widths,and TM₀ mode loss is not sensitive to the change of cross section in rib waveguide with other trench widths.These findings can simplify process and improve fabrication tolerance.A directional coupler is designed by using the loss characteristics of this shallowly-etched rib waveguide on SOI.A finite element method in electromagnetic wave beam envelope interface with perfectly-matched boundary and scattering boundary is used to simulate the three-dimensional waveguides,and then a directional coupler for TM₀-like mode with low loss is designed.The gap width between waveguides is closer to the predicted value of loss theory,which indirectly proves the rationality of lateral leakage loss theory and simulation of the shallowly-etched rib waveguide on SOI with arc cross-section.