[arctux]

Chu's prize was for laser cooling, which uses a magneto-optical trap. Magneto-optical traps confine atoms by exploiting the Zeeman effect, a spatially-varying magnetic field, and a laser with a precisely-controlled wavelength tuned to be slightly red of an electronic transition. Optical traps, on the other hand, rely on the refraction of a much larger, but still microscopic, object.

Some of Chu's work uses an optical trap, but that work did not earn his prize.

[dekhn]

Thanks for that clarification.