How Photonic Chips Differ From Electronic Chips

Light carries data across a building for a small fraction of the energy that copper needs to do the same job. It is also slower than copper over the short hops on a circuit board, it cannot be held still and stored the way an electric charge can, and it has never been made into a transistor that works. Photonic chips are cut from the same polished discs of silicon that processors are cut from, in some cases in the same factories, and yet the job they do is almost entirely different. An electronic chip works by parking electric charge on a tiny patch of silicon, where the presence or absence of that charge stands for a one or a zero, and it switches that charge about using transistors. A photonic chip holds nothing at all, because what it works with is light, and light will not sit still to be held anywhere. It guides a beam along narrow channels etched into silicon and glass, then stamps data onto that beam by altering how bright it is. It can instead alter where the beam sits in its own wave cycle, a property engineers call its phase, before turning the light…