All-light sensing and communication system on chip

III-nitride multiple quantum well diodes inherently feature an overlapping region of their emission and detection spectra, which allows them to simultaneously act as light transmitters, monitors, and receivers. Here, we monolithically integrate a transmitter, a waveguide, a monitor/modulator, and a receiver into a tiny gallium nitride (GaN) chip. The operation wavelength of the photonic circuit is from 380 to 410 nm. Since both the transmitter and receiver have identical optical functionalities, bidirectional on-chip light communication is established through the same shared waveguide via a time-division multiplexing (TDM) scheme, leading to symmetric and decentralized node architectures. The monitor senses the changes in the light transmitted inside the waveguide and converts the optical signals into electrical signals. In association with a programmable circuit, feedback information is used to automatically trigger TDM communication. This self-adaptive TDM scheme enables an experimental demonstration of bidirectional communication with dynamic switching between audio and video. Furthermore, the monitor can act as a modulator to achieve multifunctional monolithic GaN photonic integrated circuits. This work paves the way for the development of all-light sensing and communication systems in chip-scale photonic platforms for diverse applications.