High-order photonic differentiator employing on-chip cascaded microring resonators.

We propose and experimentally demonstrate a high-order photonic differentiator using on-chip complementary metal oxide semiconductor-compatible cascaded microring resonators, including first-, second-, and third-order differentiators. All the microring resonator units have a radius of 150 µm and a free spectral range of 80 GHz. The microring resonator can implement the first-order derivative of the optical field near its critical coupling region. Hence higher-order differentiation can be obtained by cascading more microring units on a single chip. For the periodical Gaussian optical pulse injection, the average deviations of all differentiators are less than 6.2%. The differentiation of pseudo-random bit sequence signals at 5 Gbit/s is also demonstrated. Our scheme is a compact and low-power-consumption solution since the cascaded microring units are fabricated with compact size on the silicon-on-insulator substrate.