Slow light waveguide with low group-velocity dispersion and low loss in 2-D photonic crystal

An analysis on the transmission properties of the light in 2-D photonic crystal coupled cavity waveguide (CCW) with triangular lattice structured by columned media and air background is presented using plane wave expansion (PWE) method. The numerical simulation results show that, the group velocity of the guide model decreases quickly with increasing the distance between the defect cavities. Considering both the dispersion and loss of the CCW, it was found that when the distance between the defect cavities is taken as double of the lattice constant, the transmittance per mm of the CCW, the bandwidth and the effective group refractive index would be 47%, 1.97 GHz and 22.4, respectively. The property of group-velocity dispersion (GVD) of the slow light was analyzed. It is found that the magnitude of the GVD value in the area of slow light is 10^-2, meaning that the structure has the best slow-light characteristic and allow the slow light propagate efficiently. Based on this CCW structure a low loss optical delayer was proposed, the calculation results show that this delayer is able to achieve a delay time of 9.4 ps and a loss of lower than 1 dB.