Dynamic modulation of wideband slow light with continuous group index in polymer-filled photonic crystal waveguide

The dynamic modulation of wide bandwidth and low-dispersion slow light with continuous variation of group index n_g is realized in a polymer-filled photonic crystal waveguide (PF-PCW) with optimal structure. By adjusting the unified radius of air holes under a different refractive index of polymer in the first two rows of holes adjacent to the defect, the structure optimization of PF-PCW is first studied, then the fixed optimal structure is obtained. In the optimal photonic crystal waveguide with hole radius r₀=0.328a, a fixed refractive index n₁=1.74 of polymer in the first-row holes, and by adjusting refractive index n₂, the flattened wideband slow light with large normalized delay bandwidth product of group index from 17.15 to 55.65 has been demonstrated. Then, by filling polymer with electro-optic effect into the second-row holes, the dynamic modulation of the optimized slow light in PF-PCW is investigated. The simulation shows that the center operating frequency slightly shifts linearly to a higher one, and the average group index increases exponentially from 33.943 to 75.546 with a normalized delay bandwidth product larger than 0.3089 as the applied voltage increases. The modulation sensitivity of the average group index is about 0.3467/V when applied voltages vary from 0 V to 120 V. These results open the possibility for the dynamic control of slow light according to the practical requirements of flexibility and tunability.