Physicists Freeze Light for a Minute: How to Pause the Speed of Light

Light is constantly moving, bouncing off surfaces as it speeds through space. Now, physicists have accomplished the seemingly impossible: they've managed to halt light itself. Researchers have now looked at the potential applications of freezing light and have even managed to extend the duration of the "pause."

In order to stop light, the researchers combined various known methods in their field. More specifically, they used a glass-like crystal that contains a low concentration of ions of the element praseodymium. They also employed two laser beams. One was part of the deceleration unit while the other was meant to be stopped. The first beam was called the "control beam," which changed the optical properties of the crystal. The second beam came in contact with the crystal and the light was slowed down within it. When the physicists switched off the control beam at the same moment that the other beam was within the crystal, the decelerated beam came to a stop--for an entire minute.

Before now, only very short storage times were possible. Perturbing environments interfered with the spin wave, the magnetism of electrons, similar to how moving ships mix up waves in a lake. The information about the stored light wave was thus gradually lost. Yet these perturbations can be alleviated by applying magnetic fields and high-frequency pulses.

There's a trick to making light storage successful. It depends strongly on the parameters of the driving optical fields, magnetic fields and the high-frequency pulses. The scientists, in fact, used computer algorithms in order to calculate the best solutions during the experiment. This allowed them to optimize the laser beams so that the light was caught as long as possible.

So what can you do with stored light? The scientists plan to explore techniques for trapping light even longer, which could achieve a higher bandwidth and data transfer rate for efficient information storage by stopped light. This could drastically improve communications across the globe.

The findings are published in the journal Physical Review Letters.