Trapped light bounces through atomic lattices

In 2014, University of California, San Diego, physicist Michael Fogler and colleagues demonstrated that light could be stored within nanoscale granules of hexagonal boron nitride. Now Fogler’s research group has published a new paper in Nano Letters that elaborates how this trapped light behaves inside the granules.

The particles of light phonon polaritons are said to disobey standard laws of reflection as they bounce through the granules, but their movement isn’t random. Polariton rays propagate along paths at fixed angles with respect to the atomic structure of the material, Folger’s team said. That in turn can lead to “interesting resonances”.

“The trajectories of the trapped polariton rays are very convoluted in most instances,” Fogler said in a statement. “However, at certain…frequencies they can become simple closed orbits.”

When that happens clusters of strongly enhanced electrical fields can emerge. Fogler’s group found those could form elaborate geometric patterns in granules of spheroidal shape.

The polaritons are not only particles but also waves that form interference patterns. When overlaid on the hot contours of enhanced electrical fields, these create strikingly beautiful images.