Effect of rotating cavities on the group velocities of the coupled-resonater optical waveguides

In this article，the influence of cavity rotation on the group velocities of the coupled-resonator optical waveguides，which consists of the two-dimensional square-lattice photonic crystal，is studied theoretically by the multiple-scattering method and the finite-difference time-domain method. Simulation results show that the original single propagation mode becomes two modes when the cavities within the waveguide are rotated alternately，and the group velocities of the modes is reduced greatly. When the rotated angle of the selected cavities is 45°，the group velocities of the propagating modes can be reduced by one order of magnitude. Compared with that of the coupled-resonator optical waveguide without rotation of selected cavities，the two velocities get their minimum value，which are 0.0016 c and 0.0009 c respectively. The difference between them is determined by the symmetry of the propagating modes.