THE UNIVERSITY of Paderborn’s Ralf Wehrspohn is one of Germany’s youngest physics professors and an expert in manipulating light. One key to future optical devices could be crystals made from materials such as silicon or aluminum oxide. Four years ago, at the Max Planck Institute, Wehrspohn constructed and patented a stamp- like tool embossed with billions of microscopic pyramids that impose a grid of tiny perforations on the materials. He and his colleagues then used acids to burrow into the perforations, creating a perfect array of holes. They melted a metal or polymer over the template, forming nanotubes of specific depths and widths in the holes. Light passing through the resulting nanoarray can be “steered” by electrical fields. Wehrspohn is now collaborating with Infineon Technologies to develop an all-optical chip that reroutes communications signals faster than current routers. He is also working on a compact sensor that measures how light flow is altered by alcohol in a person’s breath.