Delay Time Enhanced Flat Band Photonic Crystal Waveguides with Capsule- shaped Holes on Silicon Nanomembrane

摘要

A slow group velocity and low group velocity dispersion photonic crystal slab waveguide is designed by using capsule shaped air holes in hexagonal lattice. The theoretical study shows that adjusting the aspect ratio of holes in the innermost rows can fine tune the dispersion tail. The presented design can achieve nearly flat band photonic crystal waveguides with group index of 21-36 over the normalized bandwidth (delta omega/omega) of 1.38% approximately 0.4%. We also discuss the effects of the change in the holes' aspect ratio combined with a slight size adjustment. The group index in the range of 21 approximately 43 for normalized bandwidth of about 1.5% approximately 0.3% is obtained with the combination effect. The optimized designed exhibits a nearly constant group index of 21 over 22.7 nanometer bandwidth at lambda=1.55 micrometers.