Researchers in Trento report a tiny silicon device that behaves like an artificial nerve cell made of light. The building block is a photonic microresonator: a microscopic loop that holds light and lets it circulate. The loop produces pulses that are the analogue of the spikes that biological neurons use to send messages.
Living neurons are one-sided: signals mainly go from input toward output. The new work tries to give a light circuit that same one-way character.
The device is called DRUM, short for Dynamically Reconfigurable Unified Microresonator. It is a silicon ring joined to two side lobes. Driven from one side, the ring stores energy until it fires a train of spikes. Driven from the other side, it stays silent even when the incoming power is raised well above the usual firing point.
How heat retunes the neuron
The heaters also move the power level at which firing starts, change how long incoming light is gathered before a spike leaves, and stretch the quiet interval after a spike. A numerical model that mixes heating in silicon with free-carrier effects, meaning the extra charge that light creates in the material, matches the measured behavior.
Each spike still leaves a weaker beam heading backward. That return light is called back-action. In biology, signals can also travel backward from the output of a cell toward its input and help regulate later firing. In DRUM, the strength of this return beam can be set electrically.
Simulations of two DRUMs on one shared waveguide show that the return beam from one ring can make the other fire, stop its pulsing, or lock both into the same rhythm. Those three outcomes stand in for excitation, inhibition, and synchronization, without an extra part between the two rings.
The devices are made in silicon with standard chip methods and use the material’s own nonlinear response rather than an added optical amplifier. The authors argue that programmable directionality could limit unwanted feedback as such circuits grow, and that one reconfigurable part can cover jobs that used to need several different devices.