Numerical analysis of silicon-on-insulator ridge nanowires by using a full-vectorial finite-difference method mode solver

Abstract

The characteristics of silicon-on-insulator (SOI) ridge waveguides are analyzed by using a cylindrical full-vectorial finite-difference method mode solver with a perfectly-matched layer treatment. First, the single-mode condition for an SOI ridge nanowire with different Si core thicknesses is obtained. The obtained single-mode condition is different from that for the conventional micrometrical SOI ridge waveguides with a large cross section. By adjusting the cross section (the core width and the etching depth), one can have a nonbirefringent SOI ridge nanowire. The analysis on the bending loss of SOI ridge nanowires shows that one can have a relatively small bending radius even with a shallow etching (i.e., a small ratio γ between the etching depth and the total thickness). For example, even when one chooses a small ratio γ=0.4, one still has a low bending loss with a small bending radius of 15 μm for an SOI nanowire with a thin core hco=250 nm, which is very different from a conventional large SOI ridge waveguide.