Full C-band Si photonic crystal waveguide modulator.

The slow-light effect in silicon lattice-shifted photonic crystal waveguide (LSPCW) Mach-Zehnder modulators allows compact phase shifters, while limiting the working spectrum Δλ. We optimized the structural parameters of the LSPCW and extended Δλ to cover the full C-band in exchange for moderately decreasing the group index ng. We obtained Δλ=42  nm with ng=8-9 in a fabricated device and observed 25 Gbps eye opening in the 200 μm modulator in the full C-band.