ABSTRACT
Directional Waveguide Couplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Optical slow-wave structures such as coupled photonic crystal cavities, coupled microrings, coupled quantum wells, etc. are promising candidates for slow light devices because of the nature of their dispersion relationship which follows the tight-binding model well-known in solid-state physics. In a perfectly uniform structure, the slope of the dispersion curve, which defines the group velocity, is zero at the edges of the waveguide band, leading to slow light and enhanced light-matter interaction. Although the effects of group velocity dispersion (and higher-order dispersion) can limit the performance of slow light structures [1-4], the effects of dispersion can, in principle, be compensated by a variety ofmechanisms, including some ofwhich are used commonly in optical fiber communications.
