At first glance, silicon makes lousy photonic devices. Although it transmits microwaves, it doesn't lase efficiently, nor do its optical properties change readily in response to an electric field. But Si has one big advantage. Thanks to the electronics industry's 50‐year investment in the material, devices made from Si are cheap, powerful, and versatile. If Si‐based devices could manipulate photons, computers could tap directly into the optical lines that carry gigabytes of data per second. You could download a full, high‐definition movie to your PC in seconds.