Narrow-band microcavity waveguides in photonic crystals

A novel device, formed by a widely spaced periodic array of defects in a ph otonic. bandgap crystal, is studied with the goal of designing a waveguide with a prescribed narrow bandwidth. Tunneling of radiation between the defe ct sites allows wave propagation along the line of the defects. An analytic al study based on the weakly coupled cavity model is performed, and the dis persion relation omega(beta) of the new waveguide is derived. The frequency shift and the band structure of the periodic defect waveguide are linked b y an analytic relationship to the distance between the defect sites and the refore can be tuned by varying the latter. Sections of such waveguides can be employed as ultra-narrow-band filters in optical routing devices, Numeri cal simulations demonstrate the performances of this new device and support the analytical predictions. (C) 2001 Optical Society of America