Defect studies in a one-dimensional photonic band gap structure

We calculate defect modes in a finite one-dimensional quarter-wavelength stack by the transfer matrix technique, and find that the defect mode frequency depends on the refractive index as well as on the thickness of the defect layer and the transmission coefficient depends on its position. Then, by using the extended-beam-propagation method, we investigate the short pulse transmission. It is found that the amplitude of the electromagnetic field in the defect layer is much larger than that of the incident light, which can be used to enhance nonlinear effects if the defect layer is replaced by a nonlinear material.