Unidirectional light propagation characters of the triangular-lattice hybrid-waveguide photonic crystals

The high-contrast unidirectional light transport through the two-dimensional triangular-lattice photonic crystal structures is numerically studied by the finite-difference time-domain method. Through utilizing the modal match and mismatch of the waveguides to the incident light beams, and adjusting the coupling region connecting the two waveguides with different symmetric guiding modes, the unidirectional light propagation for the fundamental even-symmetric light beam is achieved. And the unidirectional light beam propagations within two different wavelength regions along the same and opposite directions are both obtained through the optimized hybrid-waveguide structures. The influence of the air holes’ radius disorder existing inevitably in the actual fabrication process to the unidirectional light transport character of the proposed structures is also studied.

•Unidirectional light propagation in the hybrid-waveguide structures is obtained.•Unidirectional light propagations towards two opposite directions are acquired.•Unidirectional propagation is designed by altering two guiding modes’ symmetry.