Abstract
Although gigahertz-scale free-carrier modulators have been demonstrated in silicon, intensity modulators operating at terahertz speeds have not been reported because of silicon’s weak ultrafast nonlinearity. We have demonstrated intensity modulation of light with light in a silicon–polymer waveguide device, based on the all-optical Kerr effect—the ultrafast effect used in four-wave mixing. Direct measurements of time-domain intensity modulation are made at speeds of 10 GHz. We showed experimentally that the mechanism of this modulation is ultrafast through spectral measurements, and that intensity modulation at frequencies in excess of 1 THz can be obtained. By integrating optical polymers through evanescent coupling to silicon waveguides, we greatly increase the effective nonlinearity of the waveguide, allowing operation at continuous-wave power levels compatible with telecommunication systems. These devices are a first step in the development of large-scale integrated ultrafast optical logic in silicon, and are two orders of magnitude faster than previously reported silicon devices.
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Acknowledgements
We gratefully acknowledge research support from the National Science Foundation Center on Materials and Devices for Information Technology Research (CMDITR), through grant DMR-0120967 by the AFOSR under contract F49620-03-1-0418, and by Boeing under the SRDMA program. We also thank the Department of Homeland Security and the National Science Foundation for generous support through graduate research fellowships. Finally, we would like to thank the Kavli Nanoscience Institute, where the devices described in this work were fabricated.
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Hochberg, M., Baehr-Jones, T., Wang, G. et al. Terahertz all-optical modulation in a silicon–polymer hybrid system. Nature Mater 5, 703–709 (2006). https://doi.org/10.1038/nmat1719
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DOI: https://doi.org/10.1038/nmat1719
