Can a magnet bend light?

In semiconductors, the flow of electrons is specifically directed and regulated with small switching voltages. For light, photonic crystals can take over this control.

Karlsruhe - German physicists have now developed such a light guide for the first time, which can be specifically influenced not by electrical voltages but by an external magnetic field. Their result, which they present in the journal "Physical Review Letters", could lead to new components for extremely fast light chips of the future.

"Our discovery is proof that magnetic photonic crystals work," says Stefan Linden from Forschungszentrum Karlsruhe. Together with colleagues from Karlsruhe University, they built so-called metamaterials on the basis of nanostructured gold wires, separated by a 50 millionth of a millimeter thin layer Magnesium fluoride, the nanowires form a photonic crystal with which the propagation of visible light waves can be controlled. If the external magnetic field is changed, the paths of the light waves also vary.

Such effects are considered essential for the construction of photonic circuits, which can process data much faster than today's electronic semiconductor modules. Until now, scientists have only used electrical controls for these photonic crystals, but control via magnetic fields opens up additional, elegant switching options. According to Linden, however, there is still a long way to go before technical applications are achieved. In his next experiments, he wants to build three-dimensional photonic crystals in order to be able to control individual light waves in all spatial directions by means of a magnetic field.