Propagation losses in silica-on-silicon optical waveguides - Theoretical analysis and comparison with expermental results

Silica-on-silicon optical waveguides are being increasingly used for me des ign and fabrication of a large variety of optical integrated circuits for a pplications in optical communication systems. One of the crucial factors in the configuration of these waveguides is the minimum thickness of the buff er layer of silica [ between the guiding core layer of doped silica and the silicon substrate ] that is required in order to keep the propagation loss of a guided mode, launched in the core and leaking into the substrate, bel ow a specified limit. An earlier analysis by Stutius et al. involved the so lution of a complex eigenvalue equation and a perturbation method to calcul ate the propagation loss in this waveguide structure. Ghatak et al. develop ed a novel 'leaky mode' analysis and a matrix method of numerical analysis to study the propagation of a mode in leaky waveguide structures. The metho d of Ghatak er al, has been applied in this paper to calculate the propagat ion losses in silica-on-silicon waveguides, and the results are found to be identical to those obtained by the earlier approach of Stutius et al. The results of calculations by different methods are also compared with experim ental results for some typical waveguides.