Novel Kind of Semislow Light Photonic Crystal Waveguides With Large Delay-Bandwidth Product

A novel type of semislow light photonic crystal waveguide obtained by shifting the boundaries of a W1 waveguide in the direction of light propagation is presented. The structure produces unusual "U-type" group index -frequency curves, which results in a nearly constant group index ng over large bandwidth. A versatile control of ng (11 <; n_g 210) with large normalized delay-bandwidth products ranging from 0.1363 to 0.3141 is obtained at the wavelength of 1550 nm using a unique geometrical parameter. Additionally, depending on the chosen waveguide geometry, ultralow group velocity dispersion (GVD) values in large slow light bandwidth can be achieved, with controllable positive or negative GVD.