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The direct butt-joint coupling between the Si-wire-based Michelson interferometer (MI) and the InGaAs/AlAsSb quantum-well waveguide was performed to realize the hybrid integrated ultrafast intersubband transition switch. By attaining the narrow gap between the waveguides, we have observed the Michelson interference spectra between the two signal lights: one is the phase modulated light from the InGaAs/AlAsSb quantum-well waveguide and the other is the light returned from the Si loop mirror of MI. Furthermore, by controlling the phases and powers of two signal lights with the thermooptic phase shifter and variable coupler in MI, we have demonstrated the ultrafast all-optical gating operation with a response time of 2 ps. The all-optical gating switch with a small size of 0.3 mm 2.35 mm was successfully fabricated by the hybrid integration technologies of III-V and Si materials.