Photonic band gap materials attracted much attention in the context of designing optical and microwave devices. Recently, numerical experiments have shown that line defects in photonic crystals can be used not only to guide but also to multiplex and demultiplex optical signals [1]. Most researchers snidying the wave guiding by line defects employ photonic wavegiudes obtained by removal of consecutive posts in the periodic structure. The strong coupling between the adjacent defects produces relatively wideband waveguides. A new guiding device with a prescribed center frequency and narrow bandwidth the Coupled Cavity Waveguide (CCW) has been proposed recently by few researchers in different independent works, and for different applications [2]-[4]. In these devices a wave-guide is formed by widely spaced periodic defects in the photonic crystal. Each defect site with a resonant frequency in the band gap serves as a micro-cavity. Tunneling of radiation between the defect sites allows wave propagation along the line of defects. Sections of such wave-guides can be employed as ultra narrow band filters in optical routing devices. A schematic description of the CCW in a two dimensional photonic crystals is shown in Fig. 1.
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