Ultrafast optical modulation using slow light photonic crystal waveguides

All-optical switching provides the ultimate speed of telecommunication. The quest for an ultrafast all-optical photonic integrated circuit requires the control over individual optical pulses. Photonic crystal (PhC) waveguides are promising building blocks of such optical circuits because their dispersion properties can be tailored and they, amongst other things, enable the slowdown of light [1]. By optically pumping a silicon photonic crystal waveguide, free carriers are generated [2] and the band structure can be shifted in an ultrafast manner [3]. In this work we use ultrafast pump-probe measurements to demonstrate a slow light PhC optical modulator that is based on free-carrier dispersion, and which operates in transmission.