High-Performance Graphene-on-Silicon Nitride All-Optical Switch Based on a Mach–Zehnder Interferometer

We propose and experimentally demonstrate a high-performance graphene-on-silicon nitride (Si3N4) all-optical switch based on a Mach-Zehnder interferometer (MZI). In our device, the graphene overlaying on a Si3N4 waveguide absorbs part of the pump light power and generates heat. Then, the Si3N4 waveguide underneath can be heated and its refractive index can be changed due to the thermo-optic effect. In this way, the phase of the probe light in the Si3N4 arm with graphene on top is tuned and all optical switching can then be implemented. In the experimental demonstration, an all-optical switch with a chip size of ~0.36 mm ² is realized with an extinction ratio of 11 dB. The tuning efficiency is measured to be 0.00917 π/mW, which is insensitive to the wavelength of the pump light. All-optical switching is also demonstrated, while the rise and fall time constants are measured to be 571 ns and 1.29 μs, respectively. These results show that our proposed configuration provides a functional integrated component for the development of efficient all-optical control devices with a fast switching speed on the insulator platform. Moreover, by using integrated MZI structure, our design could potentially achieve a broad bandwidth.