Figure 1 : Si-SiO2 slot waveguide geometry; the rails are made of Si while the substrate and BOX are made of SiO2.

From: Polarisation independent silicon-on-insulator slot waveguides

Figure 1

The geometric parameters are the height h, widths of the rails wleft and wright, slot width slot, slant angle θ, and the bending radius (radius of curvature). For waveguides with slanted walls, the slot was measured between the top of the rails, that is, where the separation between the waveguides is largest. For bent waveguides, the bending radius was taken to be the distance between the centre of curvature and the middle of the slot.