The lower image shows light flowing around an obstacle
Light readily bounces off obstacles in its path. Some of these reflections are captured by our eyes, thus participating in the visual perception of the objects around us. In contrast to this usual behavior of light, MIT researchers have implemented for the first time a one-way structure in which microwave light flows losslessly around obstacles or defects. This concept, when used in lightwave circuits, might one day reduce their internal connections to simple one-way conduits with much improved capacity and efficiency.
The laws of nature that govern the world around us allow for the propagation of light in both directions. If a light beam is observed propagating in a particular direction, one can also shine a light beam to propagate in the opposite (backward) direction. “The very fact that reflected beams are allowed to exist, combined with the fact that light at least partially reflects from most objects it encounters, makes optical reflections ubiquitous in nature,” said MIT physics Professor Marin Soljačić, the senior author of the study.
In a dramatic departure from this common phenomenon, a team made up of MIT physicists…have implemented and experimentally tested so-called topological photonic crystals that completely prohibit the existence of any lightwave back-reflections. The results, published in the 8th October 2009 edition of Nature, show the first experimental observation of the fascinating new phenomena and capabilities associated with microwave light propagating in this uniquely designed waveguide (a tunnel or “road” for guiding light).
Through the application of an external magnetic field, this specially designed waveguide induces unusual restrictions to the propagation of the light inside it. “We have now found a way to make light travel without bouncing back…”
The possibilities are infinite.