Abstract
Si-based electronic-photonic integrated circuits (EPICs), which are compatible with state-of-the-art complementary metal-oxide-semiconductor (CMOS) processes, offer promising opportunities for on-chip mid-infrared (MIR) photonic systems. However, the lack of efficient MIR optical modulators on Si hinders the utilization of MIR EPICs. Here, we clearly demonstrate the Franz-Keldysh (FK) effect in GeSn alloys and achieve on-Si MIR electro-absorption optical modulation using GeSn heterostructures. Our experimental and theoretical results verify that the direct bandgap energy of GeSn can be widely tuned by varying the Sn content, thereby realizing wavelength-tunable optical modulation in the MIR range with a figure-of-merit of Δα /α0 (FOM) greater than 1.5 and a broadband operating range greater than 140 nm. In contrast to conventional silicon-photonic modulators based on the plasma dispersion effect, our GeSn heterostructure demonstrates practical and effective FK MIR optical modulation on Si and helps unlock the potential of MIR EPICs for a wide range of applications.
Silicon-based heterogeneous photonic integrated circuits for the mid-infrared
