Efficient low-loss InGaAsP/Si hybrid MOS optical modulator

An optical modulator integrated on silicon is a key enabler for high-performance optical interconnects(1-6). 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(7,8). 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 (refs 9,10). The presented modulator exhibits a phase-modulation efficiency of 0.047 Vcm and low optical attenuation of 0.23 dB at pi phase shift at 1.55 mu m wavelength, which are approximately 5 times higher and 10 times lower than Si MOS optical modulators(11-17), respectively. This approach provides a new, high-performance phase-modulation scheme for Si photonics.