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We present the design, fabrication and characterization of athermal nano-photonic silicon ring modulators. The athermalization method employs compensation of the silicon core thermo-optic contribution with that from the amorphous titanium dioxide (a-TiO(2)) overcladding with a negative thermo-optic coefficient. We developed a new CMOS-compatible fabrication process involving low temperature RF magnetron sputtering of high-density and low-loss a-TiO(2) that can withstand subsequent elevated-temperature CMOS processes. Silicon ring resonators with 275 nm wide rib waveguide clad with a-TiO(2) showed near complete athermalization and moderate optical losses. Small-signal testing of the micro-resonator modulators showed high extinction ratio and gigahertz bandwidth.

We review the recent development of a high-speed silicon optical modulator based on electric-field-induced carrier depletion effect in a silicon-on-insulator waveguide containing a reverse-biased p-n junction. The device design, fabrication and characterization are presented. To obtain efficient optical modulation, we design a sub-micrometer size silicon waveguide phase shifter based on both semiconductor device modeling and photonic circuit modeling. By employing traveling-wave drive that allows co-propagation of electrical and optical signals along the waveguide, we demonstrate a high-frequency modulator with 3 dB optical response bandwidth of 30 GHz and data transmission up to 40 Gb s −1 . Such a high-speed silicon modulator will be a key component for silicon-photonic-integrated circuits for future computing I/O applications.

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