Yoshiteru AMEMIYA, Tomohiro TOKUNAGA, Yuichiro TANUSHI^*, and Shin YOKOYAMA^†

Research Institute for Nanodevice and Bio Systems, Hiroshima University, 1-4-2 Kagamiyama, Higashihiroshima, Hiroshima 739-8527, Japan

(Received October 20, 2008; Accepted January 27, 2009)

Electric-field drive optical modulators using a Si ring resonator were fabricated on silicon-on-insulator (SOI) wafers. The fabricated resonators consisted of Si waveguides with width and thickness of 1.0 and 0.3 μm, respectively. In order to induce the linear electro-optic (EO) effect in the Si core layer, the strain was applied by covering the layer with Si₃N₄ film (0.26 μm thick) deposited by low pressure chemical vapor deposition (LPCVD) at 750 °C. The vertical electric-field was applied to the Si waveguide through the top and bottom cladding layers, and the optical output from the drop port at the resonance wavelength was measured. At a wavelength of 1501.6 nm, the optical modulation of 33% was obtained at 200 V (electric-field at the silicon surface ∼3×10⁵ V/cm, nearly the breakdown field). The resonance wavelength was shifted toward the short wavelength side by applying both positive and negative voltages, this shift was explained by carrier concentration modulation. The linear EO effect in the Si core layer was not observed, presumably because the strain in the Si core layer was too small.

Key words: Si ring resonator, optical modulator, electric-field drive, carrier concentration modulation, electro-optic effect, optical interconnection

^*Present address: Institute for International Advanced Interdisciplinary Research, International Advanced Research and Education Organization, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
^†E-mail address: yokoyama-shin@hiroshima-u.ac.jp