Slow light to reduce the energy dissipation of Mach-Zehnder modulators in silicon photonics

Integrated Mach-Zehnder (MZ) modulators are important components in silicon photonic devices that rely on a reverse-biased p-n junction to modulate the optical signal via a change of the waveguide refractive index. Reducing their energy consumption is a crucial step towards the application of silicon photonics, especially in connection with the growing traffic volumes in data centers. In this work, we combine band-edge slow light structures consisting of silicon grating waveguides with periodic (interlaced) p-n junctions to maximize spatial matching between the optical field mode and the depletion region of the p-n junction. The two effects together will result in an improved modulation efficiency, leading to a strongly reduced energy dissipation per bit