Straight and bended high refractive index rib waveguides – theoretical analysis

This paper raises two questions concerning guiding properties of silica-titania rib waveguides. The first one is a relationship between silica-titania rib waveguides morphological parameters and their single mode operation regime. A set of these parameters includes rib height t , width w and a thickness h of a parent slab waveguide. It was shown that if a parent slab waveguide thickness is equal or higher to the value which maximizes homogeneous sensitivity of a fundamental TM mode then, depending on a value of rib width, there can be single or double range of rib height values for which the rib waveguide is single modal for quasi-TM modes. The second issue concerns an analysis of a magnitude of bend losses. It was shown that a magnitude of bend losses in silica-titania rib waveguides can be small enough allowing their application in designing of planar integrated optical circuits. The magnitude of bend losses is significantly decreased when slab waveguides adjacent the rib are cut-off.