Dispersion-controlled optical group delay device by chirped photonic crystal waveguides

Previously, we proposed and demonstrated chirped photonic crystal waveguides, in which some structural parameters are gradually changed so that the photonic band characteristic is smoothly shifted. In this letter, we discuss an optical delay line composed of two index-chirped waveguides in a directional coupler structure. A large delay is realized by a low average group velocity of $<c∕350$ near the band-edge with almost perfect dispersion compensation even for a short optical pulse. Finite difference time domain simulation demonstrates that such a device is possible in a practical design.