Novel Tapers for Slow-Light Coupling in Photonic Crystal Waveguides

In this work, the novel photonic crystal tapers have been designed for coupling of light from ridge access waveguides into photonic crystal waveguides in slow-light regime and their performances have been analyzed with a finite-different time-domain method. In our proposed tapers, the background photonic crystal is kept uniform and thus, it is simpler to design photonic crystal structures composed of a mixture of slow-light waveguides and normal waveguides. Several different tapers are tested. The width of the ridge access waveguide and surface termination of the photonic crystal are also optimized. One can see that coupling efficiencies improve from about 40% to 95% at the frequencies at which group indices are 200.