Design of large-bandwidth single-mode operation waveguides in silicon three-dimensional photonic crystals using two guided modes.

We report on the design of silicon three-dimensional (3D) photonic crystal (PC) waveguides with a combination of acceptor-type and donor-type line defects. Tuning the width of the acceptor-type line defect allows the waveguide to support two guided modes, which enable single-mode propagation over 98.7% of the complete photonic bandgap (cPBG). In addition, we demonstrate that the frequency ranges for single-mode propagation can be extended to the entire range of the cPBG by further tuning the thickness of the layers in which the donor-type line defects are located. The wide ranges of available frequencies for single mode propagation enable flexible design of 3D PC components and will provide a route towards future 3D photonic circuits.