Ultra-slow light with high NDBP achieved in a modified W1 photonic crystal waveguide with coupled cavities

Here, a modified W1 photonic crystal waveguide consisting of silicon rods arranged in a hexagonal lattice in the air is investigated for the aim of obtaining highly flattened defect band under the light line. This condition results in achieving ultra-low group velocity and suppresses the out of plane scatterings, simultaneously. The presented waveguide which is composed of the periodic coupled cavities inside the channel, provided high time delay with group index of ng∼647 and improved normalized delay bandwidth product of ∼0.54 for the propagating wave. A group velocity of about ∼0.001545c is achieved by immersing the rods with the optimized radius and periodicity of r=0.2a and 3a into the center of the channel, respectively. The PWE and the FDTD results with slight discrepancy, present the feasibility of ultra-slow light phenomenon in the presented structure.