Chirp analysis of low-power CMOS nanophotonic modulators

© 2019 IEEE.Complementary metal-oxide semiconductor (CMOS) provides an infrastructure for the implementation of a range of integrated photonic modulators, devices and circuits that have the potential to replace the state-of-the-art commercial optical modulators in long-haul communications. An important property of modulators when amplitude modulation is used is their chirp because it affects the effective transmission distance in long-haul optical fiber systems. In this paper we analyze, by the use of simulation, the chirp of CMOS microring modulators operating in the three possible coupling regions named over-coupled, hybrid-coupled, and under-coupled. We used a method that measures the small-signal frequency response of a light emitter, a modulator, a dispersive medium and a light receiver. To quantify the chirp for the large-signal modulation we used the on/off ¿-parameter calculation, the method is easy, quick, and accurate in calculating the chirp parameter. The numerical results at a wavelength of 1545.3 nm indicate an effective chirp parameter in the range of -2.2 to -0.4 when the ring is over-coupled, when the ring is hybrid-coupled the chirp is 0.63, and when the ring is under-coupled the chirp is in the range of 1.2 to 2.