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Nano Lett. 2015 Apr 8;15(4):2304-11. doi: 10.1021/nl504389f. Epub 2015 Mar 5.

Plasmonic nanostructured metal-oxide-semiconductor reflection modulators.

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†School of Electrical Engineering and Computer Science, University of Ottawa, 800 King Edward Avenue, Ottawa, Ontairo K1N 6N5, Canada.
‡Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur Streey, Ottawa, Ontairo K1N 6N5, Canada.
§Department of Electronics, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
∥Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5, Canada.
⊥Centre for Research in Photonics at the University of Ottawa, 800 King Edward Avenue, Ottawa, Ontario K1N 6N5, Canada.


We propose a plasmonic surface that produces an electrically controlled reflectance as a high-speed intensity modulator. The device is conceived as a metal-oxide-semiconductor capacitor on silicon with its metal structured as a thin patch bearing a contiguous nanoscale grating. The metal structure serves multiple functions as a driving electrode and as a grating coupler for perpendicularly incident p-polarized light to surface plasmons supported by the patch. Modulation is produced by charging and discharging the capacitor and exploiting the carrier refraction effect in silicon along with the high sensitivity of strongly confined surface plasmons to index perturbations. The area of the modulator is set by the area of the incident beam, leading to a very compact device for a strongly focused beam (∼2.5 μm in diameter). Theoretically, the modulator can operate over a broad electrical bandwidth (tens of gigahertz) with a modulation depth of 3 to 6%, a loss of 3 to 4 dB, and an optical bandwidth of about 50 nm. About 1000 modulators can be integrated over a 50 mm(2) area producing an aggregate electro-optic modulation rate in excess of 1 Tb/s. We demonstrate experimentally modulators operating at telecommunications wavelengths, fabricated as nanostructured Au/HfO2/p-Si capacitors. The modulators break conceptually from waveguide-based devices and belong to the same class of devices as surface photodetectors and vertical cavity surface-emitting lasers.


Surface plasmon; grating; modulator; oxide; silicon


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