Add-Drop Microring Resonator Switch With Positive/Negative Phase Tuning Using InGaAsP/Si Hybrid MOS Phase Shifter

We successfully demonstrated an add-drop Si microring resonator switch using an InGaAsP/Si hybrid metal-oxide-semiconductor (MOS) optical phase shifter. We revealed that a Si shallow rib waveguide is effective to achieve a quasi-single-mode microring resonator, even when employing a 200-nm-thick InGaAsP membrane on the Si ring waveguide. Owing to the careful design in the Si waveguide, we experimentally demonstrated the well-behaved add-drop switching operation using the InGaAs/Si hybrid MOS phase shifter with a modulation efficiency of 0.53 Vcm. The integration of a 200-nm-thick InGaAsP enabled both positive and negative phase tuning through carrier accumulation and depletion at the InGaAsP MOS interface. As a result, the modulation efficiency was improved by a factor of 7.5, compared to the hybrid MOS phase shifter utilizing a 25-nm-thick InP membrane. With an insignificant gate leakage current, we achieved an exceptionally low switching power of 150 fW. Additionally, the measured switching time was less than 6 ns. These characteristics make the demonstrated add-drop microring resonator switch highly promising for wavelength division multiplexed programmable photonic integrated circuits.