Donuts and laser beams

In materials research, considerable progress is made by exploiting insights from the field of topology. Similar tools can now be applied to lasers.

A donut is not a bun. From a mathematical point of view, they are two fundamentally different objects: The donut has a hole, the bun does not. A circle inside the donut around its hole in the center cannot be shrunk to a point. An arbitrary circle inside the bun, however, can.

The mathematical discipline that deals with such categorizations of surfaces and bodies is topology. In recent years, its role in physics has also increased: in 2016, the Nobel Prize was awarded for the application of topological concepts to solid-state physics. Now it turns out: topology can also play a crucial role in the generation of laser light. A collaboration between the Technical University of Vienna (TU Wien) and research teams from the USA has led to the development of a special laser that emits light beams with characteristic topological properties. This success has now been published in the journal “Science”.