Some photons zoom along thoroughfares.
Others navigate the city's streets, making hard right and left turns. The buildings lining the streets house still other photons that, like a fleet of taxis, are fueled and ready to be called into service. Already materials fabricated with the photonic crystals simulated by Joannopoulos's group are reducing the amount of light lost when it is squeezed into a small space or when a cable makes a 90-degree turn. In the material being tested by Joannopoulos's collaborators, light is transmitting around these corners with 98 percent efficiency. This tighter control, says Joannopoulos, is what could make structures like those he is simulating mainstays of the miniature optical devices of the future.