GaAs/Si hybrid mode photonic crystal nanobeam cavity for saturable nonlinearity

Silicon photonics is an excellent platform for high yields and seamless on-chip integration with electronics, low-power consumption, and low-cost manufacturing. However, silicon has a small nonlinear optic coefficient, and it is challenging to realize nonlinear optical response, which is essential for versatile phenomena that linear systems cannot provide. As an alternative, III-V semiconductor offers significant nonlinear behavior based on quantum well or quantum dot structures. Hybrid integration of III-V semiconductor into silicon photonic circuit ensures to combine those two functionalities. Still, designing a cavity incorporating hybrid-mode in both Si and GaAs has not been done. This work presents a GaAs/silicon photonic crystal cavity with a gallium arsenide plate on top of a silicon cavity based on hybrid-mode using 3D FDTD simulation at telecom wavelength. On-resonance nonlinear transmission based on saturable absorption is obtained by embedding InAs quantum dots in the GaAs region. Our hybrid-mode cavity is easy to fabricate without precise Si/GaAs alignment, and it has low threshold power under continuous wave (CW) operation and high on-resonance transmission.