Properties of two-dimensional photonic crystals with defects

Photonic crystal is a periodic optical structure in which the refractive index changes periodically. In recent years, PC-based optical devices have received considerable attention due to their interesting characteristics, such as their small size, photonic band gap, negligible loss in micrometer range, extremely low group velocity, flexibility in shape and dimensions, improved frequency-dependent selection and applicability in photonic integrated circuits (PICs). Many optical devices based on PC structures, have been submitted, such as optical filters, microcavities, power splitters , optical switches [5, 6], optical circulators, demultiplexer, and triplexer.