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Efficient low-loss InGaAsP/Si hybrid MOS optical modulator:Associate Professor Mitsuru Takenaka, Department of Electrical Engineering and Information Systems, and other researchers.

An optical modulator integrated on silicon is a key enabler for high-performance optical interconnects. However, Si-based optical modulators suffer from low phase-modulation efficiency owing to the weak plasma dispersion effect in Si, which also results in large optical loss. Therefore, it is essential to find a novel modulation scheme for Si photonics. Here, we demonstrate an InGaAsP/Si hybrid metal-oxide–semiconductor (MOS) optical modulator formed by direct wafer bonding. Electron accumulation at the InGaAsP MOS interface enables the utilization of the electron-induced refractive index change in InGaAsP, which is significantly greater than that in Si. The presented modulator exhibits a phase-modulation efficiency of 0.047 Vcm and low optical attenuation of 0.23 dB at π phase shift at 1.55 μm wavelength, which are approximately 5 times higher and 10 times lower than Si MOS optical modulators, respectively. This approach provides a new, high-performance phase-modulation scheme for Si photonics.

Nature Photonics :