Harnessing plasma absorption in silicon MOS modulators

High bandwidth, low power and compact silicon electro-optical modulators are essential for future energy efficient and densely integrated optical data communication circuits. The all-silicon plasma dispersion effect ring resonator modulator is an attractive prospect. However its performance is currently limited by the trade-off between modulation depth and switching speed dictated by its quality factor. Here we introduce a mechanism to leap beyond this limitation by harnessing the significant plasma absorption induced in a silicon MOS waveguide to enhance the extinction ratio of a low quality factor, high-speed ring modulator. Fabricated devices have demonstrated 20dB of electro-absorption modulation at the resonance with a 3.5V bias change and a total modulation depth of 27dB with the concurrent carrier refraction induced wavelength shift. Modulation enhancement has been observed from kHz to GHz operation with data modulation up to 100Gbit/s on-off keying demonstrated, paving the evolution of optical interconnects to 100Gbaud and beyond per wavelength.