Novel slow light waveguide with controllable delay-bandwidth product and utra-low dispersion.

We demonstrate a novel type of slow light photonic crystal waveguide which can produce unusual "U" type group index - frequency curves with constant group index n(g) over large bandwidth. By shifting the boundaries of this waveguide, flexible control of n(g) (10 <n(g)< 210) with large bandwidth (1nm<Deltalambda<43nm centered at 1550nm) and normalized Delay-Bandwidth Product (0.1363<DBP<0.3143) are achieved. Additionally, depending on the chosen waveguide geometry, extremely low group velocity dispersion (GVD<0.5 ps x nm(-1) x mm(-1)), with controllable group velocity dispersion of both signs is obtained.