Research On The Roughness Of Silicon-based Waveguide And Optical Loss Caused By Guided-wave Mode

Silicon-on-insulator(SOI)optical waveguides have been widely used in the fields of modern optical fiber communication and optical interconnection in computers.Silicon photonic devices have low production costs,reliable working performance and good compatibility with the mature microelectronics manufacturing technologies and the high-density integration,so the demand for the optical chip industry and photonic integrated circuits based on the SOI waveguides is growing rapidly.,but the light loss caused by the sidewall roughness is one of the important factors that limit the optical loss performance of the waveguide chip.In this thesis,we study the optical propagation loss(OPL)caused by the interaction between the surface roughness of the optical waveguide including SOI waveguide and silicon oxide and the optical waveguide mode.By introducing both the three-dimensional(3D)anisotropic distributed sidewall roughness(SWR)of waveguide and an interaction function between the waveguide boundaries of guide mode,the OPL is remodeled based on the Payne-Lacey(PL)theoretical model.In the PL model,since the two dimensionless functions in the structure function f_e(x,?):x and?,and the correlation length Lc determined by the waveguide structure(the width and the refractive index of silicon core)are the key parameters,the influences of waveguide structures and the structure function f_e(x,?)on the correlation length Lc are systematically simulated first.As a result,the relationship between the waveguide structure and the correlation length is found,and the dominant factor of determining the correlation length is further discovered.Subsequently,with the modified theoretical model,the synchronous dependences of OPL coefficient on the SWR and the refractive index of silicon core of the SOI waveguide are numerically simulated with respect to the typical waveguide widths,and then it is found that both the width and the refractive index of silicon core have the nonignorable effect on the OPL albeit they have very weak influences on the correlation length.Finally,two fabricated SOI optical waveguide devices are measured and the 22nm and 50nm average values of sidewall roughness(SWR)are obtained.As a result,the average OPL values at TE and TM mode are3.1 d B/cm and 4.3 d B/cm,respectively,which are consistent with the numerical simulation values.The above results are of great significance to the development of SOI waveguide devices.