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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 10 — May. 20, 2013
  • pp: 12699–12712

Theoretical investigation of ultracompact and athermal Si electro-optic modulator based on Cu-TiO2-Si hybrid plasmonic donut resonator

Shiyang Zhu, G. Q. Lo, and D. L. Kwong  »View Author Affiliations

Optics Express, Vol. 21, Issue 10, pp. 12699-12712 (2013)

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An ultracompact silicon electro-optic modulator operating at 1550-nm telecom wavelengths is proposed and analyzed theoretically, which consists of a Cu-TiO2-Si hybrid plasmonic donut resonator evanescently coupled with a conventional Si channel waveguide. Owing to a negative thermo-optic coefficient of TiO2 (~-1.8 × 10−4 K−1), the real part of effective modal index of the curved Cu-TiO2-Si hybrid waveguide can be temperature-independent (i.e., athermal) if the TiO2 interlayer and the beneath Si core have a certain thickness ratio. A voltage applied between the ring-shaped Cu cap and a cylinder metal electrode positioned at the center of the donut, − which makes Ohmic contact to Si, induces a ~1-nm-thick free-electron accumulation layer at the TiO2/Si interface. The optical field intensity in this thin accumulation layer is significantly enhanced if the accumulation concentration is sufficiently large (i.e., > ~6 × 1020 cm−3), which in turn modulates both the resonance wavelengths and the extinction ratio of the donut resonator simultaneously. For a modulator with the total footprint inclusive electrodes of ~8.6 μm2, 50-nm-thick TiO2, and 160-nm-thick Si core, FDTD simulation predicts that it has an insertion loss of ~2 dB, a modulation depth of ~8 dB at a voltage swing of ~6 V, a speed-of-response of ~35 GHz, and a switching energy of ~0.45 pJ/bit, and it is athermal around room temperature. The modulator’s performances can be further improved by optimization of the coupling strength between the bus waveguide and the donut resonator.

© 2013 OSA

OCIS Codes
(130.3120) Integrated optics : Integrated optics devices
(240.6680) Optics at surfaces : Surface plasmons
(250.7360) Optoelectronics : Waveguide modulators
(250.5403) Optoelectronics : Plasmonics

ToC Category:
Integrated Optics

Original Manuscript: January 29, 2013
Revised Manuscript: April 5, 2013
Manuscript Accepted: April 5, 2013
Published: May 16, 2013

Shiyang Zhu, G. Q. Lo, and D. L. Kwong, "Theoretical investigation of ultracompact and athermal Si electro-optic modulator based on Cu-TiO2-Si hybrid plasmonic donut resonator," Opt. Express 21, 12699-12712 (2013)

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