Time-domain research for the normal dispersion in the second photonic crystal passband

Photonic crystal (PC) has aroused the attention of people as a new type of material that can be used to control electromagnetic waves. However, there are some uncertainties about the dispersion of photonic crystal passbands. The experiments of both the time-domain and frequency-domain are studied to demonstrate the normal dispersion in the second photonic crystal passband. Within the frequency region of first and second passbands, the position and time behavior of a Gaussian modulated waveform with frequency from 0.5 GHz to 3.2 GHz is investigated and it shows that the phase velocity and group velocity are parallel along the photonic crystal transmission line (PC TL) . A couple structure composed of one-dimension photonic crystal and meta-materials realized by composite right-/left-handed transmission line (CRLH TL) is also studied, and it demonstrates the normal dispersion in the second photonic crystal passband. The experimental results of both the time-domain and frequency-domain method agree extremely well with the simulations.