A novel characterization method is proposed to extract the optical frequency field-effect mobility (μop,FE) of transparent conductive oxide (TCO) materials by a tunable silicon microring resonator with a heterogeneously integrated titanium-doped indium oxide (ITiO)/SiO2/silicon metal–oxide–semiconductor (MOS) capacitor. By operating the microring in the accumulation mode, the quality factor and resonance wavelength shift are measured and subsequently used to derive the μop,FE in the ultra-thin accumulation layer. Experimental results demonstrate that the μop,FE of ITiO increases from 25.3 to 38.4cm2?V-1?s-1 with increasing gate voltages, which shows a similar trend as that at the electric frequency.

Transparent conductive oxides have attracted escalating research interest for integrated photonic devices and metasurfaces due to the extremely large electro-optic modulation of the refractive index by the free-carrier-induced plasma dispersion effect. In this paper, we have designed and fabricated a silicon microring resonator using an indium-tin oxide gate as the electric-tuning electrode. It achieved an ultralarge resonance wavelength tunability of 271 pm/V, which is obtained through the reduced width of the ring waveguide and a high-dielectric-constant HfO2 insulator. We demonstrated a broad resonance wavelength tuning range of over 2 nm with an ultrafast response time of less than 12 ns and near-zero static power consumption, which outperforms traditional thermal tuning.