Investigation on abnormal group velocities in 1D coaxial photonic crystals

In this paper, the group velocities of electromagnetic wave for a one-dimensional coaxial photonic crystal in the stop bands with and without defect mode are studied. The results show that the group velocities exceed c (the speed of light in vac- uum) in the stop band and it tends to be very slow in the defect mode. The group velocities also are ob- tained using the method of the transmission line and transmission matrix. The simulating results agree well with the experimental.