Dual-function optical modulation and detection in microring resonators integrated graphene/MoTe2 heterojunction

On-chip photonic devices such as modulators and photodetectors are essential building blocks for integrated photonics, enabling a wide range of applications in optical communication, sensing, and other emerging fields. Generally, optical modulation and photodetection are accomplished by two discrete devices in integrated photonic circuits, prohibiting the expansion of device functionality and the miniaturization of photonic systems. In this work, we demonstrate graphene/MoTe2 heterojunction integrating with microring resonators (MRRs) to serve as an optical modulator under positive bias voltage and a photodetector under negative bias voltage at the telecom band. Such a device primarily benefits from graphene's optoelectronic characteristics, including broadband absorption and electrostatically tunable refractive index. The obtained dual-functional MoTe2/graphene heterojunction devices demonstrate a modulation depth of ∼26.7 dB, a bandwidth of 7.0 GHz, and a self-driven, wavelength-sensitive optoelectronic response at the telecom C band. Our studies indicate that combining graphene van der Waals heterojunction with MRRs paves the way to emerging photonic applications such as neuromorphic computing while expanding the freedom for miniaturized photonic circuits.