Highly efficient electro-optical phase modulation enabled by graphene
Researchers from AMO GmbH, in collaboration with researchers from IMEC (Belgium) and CNIT (Italy), have recently demonstrated that graphene enables highly efficient on-chip electro-optical phase modulators.
Phase modulators are key components in high performance optical communication systems, where they are needed to encode the electronic data stream onto the light. The key performance parameters of phase modulators are drive voltage, operation speed and insertion loss. In addition the on-chip integration of photonic components requires small devices, so that footprint is becoming more and more a decisive parameter. Graphene has already been considered as a very promising material from a theoretical perspective, as it should enable ultra-fast and ultra-efficient phase modulators with a small footprint.
In the current work M. Mohsin and colleagues perform the first experimental demonstration that the electro-refractive effect of graphene on a silicon waveguide is extremely strong (> 10−3), surpassing the current state-of-the-art by one order of magnitude. This strong electro-refractive change can be reached already at low drive voltages below 1 V. A key parameter of a phase modulator is VπL, the modulator length multiplied by the operation voltage needed to achieve a phase shift of π. A value of just 2.7 Vmm is reached in the current work, significantly outperforming state-of-the-art Silicon pn-junction based depletion type modulators. The operation of the graphene modulator has been shown at 1310 nm and 1550 nm laser wavelength, covering the most important wavelengths for optical fiber communication systems.
These results will lead to significantly reduced phase modulator power consumption and increased on-chip integration density, enabling higher data rates at lower cost.
The work was supported by the European Commission through the Flagship project „Graphene“. The work is published in two papers, which appeared recently in optics Express and IEEE Photonics Journal:
Muhammad Mohsin, Daniel Schall, Martin Otto, Bartos Chmielak, Stephan Suckow, Daniel Neumaier, “Towards the predicted high performance of waveguide integrated electro-refractive phase modulators based on graphene”, IEEE Photonics Journal, Volume 9 Issue 1, (2016)
Vito Sorianello, Gabriele De Angelis, Tommaso Cassese, Michele Midrio, Marco Romagnoli, Muhammad Mohsin, Martin Otto, Daniel Neumaier, Inge Asselberghs, Joris Van Campenhout, Cedric Huyghebaert, “Complex effective index in graphene-silicon waveguides”, Optics Express 24, no. 26, 29984-29993 (2016)