Researchers at MIT who succeeded last year in creating a material that could trap light and stop it in its tracks have now developed a more fundamental understanding of the process. The new work—which could help explain some basic physical mechanisms—reveals that this behavior is connected to a wide range of other seemingly unrelated phenomena.
The findings are reported in a paper in the journal Physical Review Letters, co-authored by MIT physics professor Marin Soljačić; postdocs Bo Zhen, Chia Wei Hsu, and Ling Lu; and Douglas Stone, a professor of applied physics at Yale University.
Light can usually be confined only with mirrors, or with specialized materials such as photonic crystals. Both of these approaches block light beams; last year's finding demonstrated a new method in which the waves cancel out their own radiation fields. The new work shows that this light-trapping process, which involves twisting the polarization direction of the light, is based on a kind of vortex—the same phenomenon behind everything from tornadoes to water swirling down a drain.
In addition to revealing the mechanism responsible for trapping the light, the new analysis shows that this trapped state is much more stable than had been thought, making it easier to produce and harder to disturb.
"People think of this [trapped state] as very delicate," Zhen says, "and almost impossible to realize. But it turns out it can exist in a robust way."
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