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Micrometre-scale silicon electro-optic modulator


Metal interconnections are expected to become the limiting factor for the performance of electronic systems as transistors continue to shrink in size. Replacing them by optical interconnections, at different levels ranging from rack-to-rack down to chip-to-chip and intra-chip interconnections, could provide the low power dissipation, low latencies and high bandwidths that are needed1,2,3,4. The implementation of optical interconnections relies on the development of micro-optical devices that are integrated with the microelectronics on chips. Recent demonstrations of silicon low-loss waveguides5,6,7, light emitters8, amplifiers9,10,11 and lasers12,13 approach this goal, but a small silicon electro-optic modulator with a size small enough for chip-scale integration has not yet been demonstrated. Here we experimentally demonstrate a high-speed electro-optical modulator in compact silicon structures. The modulator is based on a resonant light-confining structure that enhances the sensitivity of light to small changes in refractive index of the silicon and also enables high-speed operation. The modulator is 12 micrometres in diameter, three orders of magnitude smaller than previously demonstrated. Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures.

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Figure 1: Schematic layout of the ring resonator-based modulator.
Figure 2: SEM and microscope images of the fabricated device.
Figure 3: DC measurement of the ring resonator.
Figure 4: Waveforms of the electrical driving signal and the transmitted optical signal.


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This work has been partially carried out as part of the Interconnect Focus Center Research Program at Cornell University, supported in part by the Microelectronics Advanced Research Corporation (MARCO), its participating companies, and DARPA. We acknowledge support by the National Science Foundation (NSF). We thank G. Pomrenke, AFOSR, for supporting the work. We also acknowledge support by the Cornell Center for Nanoscale Systems. The devices were fabricated at the Cornell Nano-Scale Science & Technology Facility. We also thank J. Shah, DARPA, for funding this work as part of the EPIC programme.

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Correspondence to Michal Lipson.

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Xu, Q., Schmidt, B., Pradhan, S. et al. Micrometre-scale silicon electro-optic modulator. Nature 435, 325–327 (2005).

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