A Small Polymeric Ridge Waveguide With a High Index Contrast

In this paper, an optimal design of a small polymeric ridge waveguide with a high index contrast is presented. In order to reduce the leakage to the substrate and pure bending losses, the buffer layer of the present waveguide is etched partially. The single-mode condition, the bending characteristics, and the birefringence of the present small polymeric ridge waveguide are also studied. By adjusting the core width and the core height, it is possible to obtain a polarization-insensitive small polymer ridge waveguide. For the bending loss, the numerical results show that the dominant part is the transition loss between the straight and bending sections (other than the pure bending loss) and the transition loss could be reduced greatly by introducing a lateral offset. However, the transition loss is still too large to obtain a very small bending radius (e.g., 10 $mu $m). When only the pure bending loss is necessary to consider in some special case (e.g., microrings without any transitions), one can have a bending radius less than 10 $mu$m due to the possibility of low pure bending loss.