Joachim Fischer of the Karlsruhe Institute of Technology in Germany has created a fully functional invisibility cloak that works in three dimensions for all visible light, independent of its orientation. Made by using a laser to write on a special polymer, the cloak does not require light to be coming from a specific direction, or light to be within a narrow, non-visible section of the spectrum, like microwaves or infrared.
There’s just one catch.
The cloak is kind of small. And I don’t mean like… now-that-Harry-and-friends-are-fifteen-years-old-less-of-them-fit-underneath small. “Less than half the cross-section of a human-hair” small.
Fischer makes the tiny cloak—less than half the cross-section of a human-hair—by direct laser writing (i.e. lithography) into a polymer material to create an intricate structure that resembles a miniature woodpile. The precisely varying thickness of the “logs” enables the cloak to bend light in new ways. The key to this achievement was incorporating several aspects of a diffraction-unlimited microscopy technique into the team’s 3-D direct writing process for building the cloak. The dramatically increased resolution of the improved process enabled the team to create log spacings narrow enough to work in red light.
Applications of his invisibility cloak do not include sneaking around behind his teacher’s backs, but rather making very clear and small lenses for computer chips, and for making more powerful solar cells.