Cavity–Waveguide Coupling Modulation via an Optical Analogue of Superradiance in Microring Arrays

Abstract

The limitation on the modulation speed of a cavity-based optical modulator posed by cavity linewidth can be circumvented by modulating the coupling rate to the cavity. However, most coupling modulation methods cannot control this coupling rate in isolation to the cavity’s refractive index. Here, we report a method to purely modulate the coupling rate by exploiting an optical analogue of superradiance in an array of bidirectionally interacting microring cavities. Unlike existing coupling modulation schemes, our method does not require a perturbation of the cavity or the cavity–waveguide coupling region. We experimentally demonstrate coupling rate tuning in two- and three-resonator systems with a modulation range of ∼1.5 times the coupling rate of a single resonator. Both systems exhibit a linear scaling of their overall coupling rates with the number of resonators, providing direct evidence for the existence of superradiance. Furthermore, we validate the optical response of the coupled microring systems using temporal coupled mode theory. The results presented in this manuscript provide avenues for developing the next generation of highly efficient and ultrafast electro-optic modulators.