Study of Photonic Crystal Slow-Wave Circuits

In this paper, relations between photonic band gaps and operating mode of slow-wave circuits constructed by photonic crystals are discussed, and methods for computing photonic band gaps and determining the operating band are given. As an example, a slow-wave circuit containing two-dimensional photonic crystals is analyzed. The results explain that complete photonic band gap is not necessary for traveling wave tubes, and more than one defect-mode maybe coexists inside one photonic band gap. If there have no complete photonic band gap, special input and output circuits capable of customizing modes are necessary. Compared with conventional traveling wave tubes, the numerical results do not suggest the bandwidth of the photonic crystal traveling wave tube is wider, and the interaction impedance is lower. This work was supported in part by the National Natural Science Foundation of China under Grant 60532010 and 60401005. The authors are with University of Electronic Technology and Science of China, Chengdu, China, 610054.