Wideband Slow Light With Large Group Index and Low Dispersion in Slotted Photonic Crystal Waveguide

Slow light in slotted photonic crystal waveguide is a promising approach for practical applications. Two of the crucial concerns of this technology are the limited bandwidth and the pulse broadening. It was demonstrated that wideband slow light with large group index and low dispersion could be realized by shifting the first and second rows of air holes adjacent to the slot. Keeping the group index at 28, 41, and 105, respectively, the corresponding bandwidths of flat and low dispersion band could reach 17, 6.8, and 1.7 nm around 1550 nm. To further enlarge the bandwidth and group index, the oblique structure was introduced, and the bandwidths over 23.6, 6, and 1.8 nm were achieved with the group index of 30, 45, and 110, respectively. Then the propagation of slow light optical pulse was performed in time domain by the finite-difference time-domain method and a resonant structure was designed for input and output interfaces to improve the coupling efficiency.