Demonstration of complementary apodized cascaded grating waveguides for tunable optical delay lines

High-speed, tunable integrated silicon photonic delay lines are demonstrated by cascading complementary apodized silicon grating waveguides. The cascaded grating waveguides, with inward and outward super-Gaussian apodization profiles, compensate each other's dispersion and allow high-speed operation. Characterization of the compact delay lines shows that they have low loss, offer true time delays of 82 ps and a tuning range of 32 ps, and can potentially operate at bit rates as high as 107 Gb/s.