Effects of impurities on photonic band structure in coaxial photonic crystals

One-dimensional photonic crystals have been constructed by connecting segments of coaxial cable of differing characteristic impedance. Impurities have been introduced into these crystals by inserting segments of cable with lengths and/or impedances that disrupt the periodicity. This system provides a simple, inexpensive way to study one-dimensional photonic band structure effects with complete control over impurities in the lattice. We have studied in detail the effects of the size and number of defects, interaction between multiple defects, defect location in the lattice (boundary effects), the concentration of energy in the electromagnetic fields within doped crystals, and the influence of the defects on the phase (dispersion). We have used a modified dielectric stack model to simulate this system and results are in excellent agreement with the measurements.