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Optimization of a two-dimensional photonic crystal waveguide for ultraslow light propagation

A two-dimensional photonic crystal waveguide is optimized for ultraslow light propagation. By employing geometry projection method optimization, a flat band photonic crystal waveguide is achieved with the minimum group index around 2335, which is much larger than those reported before. The investigation of the transient propagation of the Gaussian pulse in the waveguide indicated that low group velocity dispersion can cause a small expansion of the pulse. The stability analysis indicates that slightly numerical and angular deviation in fabrication can influence the minimum group index of the waveguide, but the ultraslow light property can still be maintained. The theory simulation in our work can provide some useful guidance for further ultraslow light research.