Study on the Slow Light Characteristics of Low-Dispersion Photonic Crystal Coupled-Cavity Waveguide

We designed a two-dimensional triangular lattice photonic crystal coupled-cavity waveguide of four hole micro cavities.Transmission spectra of TE-polarized light are calculated by using the finite-difference time-domain(FDTD) method and slow light with a maximum group ng=1460.31 index,maximum group velocity vg=c/1460.31 at wavelength 1.55941μm are obtained.This photonic crystal coupled-cavity waveguide can produce "U" type group index-frequency curves with low dispersion slow light area at the bottom of the "U" type curves of which the central wavelength of the area is 1.55917μm,average group index g=721.92,band gap Δλ=0.35nm and flat ratio σ=0.02% by calculation.In this paper,we replace the location of first row of air hole in coupled cavity waveguide to investigate the change of low-dispersion slow light.The results not only show that the central wavelength of the area is 1.60412μm,average group index g=41.05,band gap Δλ=6.67nm but also slow light with a maximum group index ng=2173.12,maximum group velocity vg=c/2173.12 at wavelength 1.56177μm are obtained.