Design of single-mode step-tapered waveguide sections

Single-mode step-tapered waveguide sections are analyzed in an effort to determine how the various device parameters, specifically, taper function, mask spot size, and taper length, affect power loss. The results indicate that 1) for short to medium length tapers, linear tapers exhibit the lowest loss, whereas for long tapers, all of the taper functions exhibit essentially the same loss; 2) for single-mode transitions with waveguide widths in the range
2-15 \mu
m, the loss in a step-tapered waveguide section can be nearly minimized as long as the mask spot size is chosen such that there are at least 20-25 steps in the taper; and 3) the length of a given taper for minimum power loss is strongly influenced by the asymmetry of the waveguide structure.