German researchers have managed to halt the motion of light for one minute using glass-like crystals containing low concentration of ions of praseodymium.
In the experiment, they have relied on two beams of light – the first one, referred to as the control beam, passes through the crystal while changing its properties. When the second beam moves through, the modified ion structure of the crystal reduces its speed considerably. When the second beam is trapped within the crystal, the first - control - beam is switched off, resulting in the second beam slowing down even more and eventually ceasing to move completely.
Thomas Hoffman, leader of the team from the Technical University in Darmstadt, Germany, said the light basically turned into a wave trapped within the crystal lattice.
Previously, scientists have only been able to stop the motion of light for an extremely short period of time, like seconds or even less. The current breakthrough, the researchers explained, is possible thanks to unique properties of the chemical element called praseodymium.
The electrons orbiting praseodymium ions create strong spin forces similar to magnetic fields that have the power to slow down the laser beam.
During the experiment, researchers have also been able to save images transferred by the light pulse into the crystal for a minute – a million-fold improvement compared with previous experiments.
According to the researchers, the storage time of the light is limited by perturberences that disrupt the medium similarly to ships on water. Magnetic field and high-frequency pulses, however, can mitigate these perturberences to a certain extent.
The team is now working on techniques that could prolong the time for which the light is stopped and stored within the crystals. They believe it should be possible to get up to a week’s period, which would open new possibilities for future data processing based on light. After that, the team will try to increase the bandwidth used and the amount of data transferred.