Numerical analysis of silicon–clad planar optical waveguides

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AbstractThe results of the numerical calculations related to the propagation characteristics of silicon‐clad planar optical waveguides are presented. The finite‐element method is used for the calculations. First, the propagation characteristics of TE modes in waveguides of silicon layer/dielectric core/homogeneous dielectric substrate are investigated. The results are compared with those of the exact solution to confirm the correctness of the present method. In this case, the phase and attenuation constants both oscillate periodically with the silicon thickness. Then, the TM modes are analyzed and it is indicated that the propagation constants are different from those of the TE modes and that propagation constants do not necessarily oscillate periodically with the silicon thickness. Whether or not the oscillations are present depends on the refractive‐index difference between the dielectric core and the silicon layer. Next, to reduce the propagation losses of the silicon‐clad planar optical waveguides with interesting characteristics, the new structures of silicon layer/inhomogeneous dielectric substrate or silicon layer/dielectric buffer layer/ inhomogeneous dielectric substrate, are proposed. It is shown that the propagation losses of these silicon‐clad planar optical waveguides expressed in decibels, are reduced by one order of magnitude compared with the previous planar waveguides.