Experimental study and modelling of high-transmission defect modes in photonic crystals with graphite structure

The authors present an experimental demonstration and a modelling of high-transmission defect modes in graphite type photonic crystals. Such two-dimensional crystals are of interest for applications in integrated optics due to the existence of a complete forbidden band of relatively low order. Experiments are currently performed at microwave frequencies using hexagonal lattices of alumina rods to provide an easier and more accurate analysis of point defect modes. The complete photonic bandgap extends from -57 to 61 GHz. By introducing a row of vacancies in the crystal, we show that a sharp resonance can be created ill the gap with a transmission level comparable to that obtained in the neighbouring transmission bands. Besides, a sharp resonance with a transmission of -6 dB (~25%,) is obtained in the lowest forbidden band when six defects are arranged to form a small hexagonal cavity. The transmission spectra are well reproduced by numerical simulations with a finite difference time domain model which also gives the field pattern of the defect modes