Scientists develop techniques to manipulate speed of light

Speed of light measurement device
Michelson Interferometer, an optical instrument to measure the speed of light, as kept in Museum of Science and Industry, Chicago (Credits - Wikimedia Commons)

A group of researchers at the University of Central Florida have developed a technique to be able to control the velocity of light. Through this technique they can not only increase the speed of light pulse and decrease it, but they can also make it travel backwards. The results were published in Nature Communications.
This finding is a significant step in the research which can someday lead to the development of highly efficient optical communication techniques. The problems of data congestion and information loss can also be handled with this result. Currently, networks use congestion control and congestion avoidance techniques to avoid these problems. More and more devices are going online everyday and advanced techniques like these will be of prime importance in the future. With fall in the prices of data consumption, people in developing countries are getting easier access to data like never before.
There have been many attempts in the past to control the speed of light. For example, light was passed through different media to adjust the speed. The major breakthrough in this experiment is that speed of light can be adjusted in the open for the first time, without using any pass-through media to increase or decrease its speed.
Ayman Abouraddy, professor in UCF’s College of Optics and Photonics who is also a co-author of this study remarked that this is the first clear demonstration of controlling the speed of the light and this will open up many areas of possibilities not explored before. This is done in a simple, reliable and repetitive way which is an important aspect.
Scientists could speed up the light upto 30 times of its normal speed, reduce to half of the speed of light and also make the pulse travel backwards. The researchers managed to develop the technique with the help of a special device called as the phase-only spatial light modulator (SLM). This helps to combine the space and time properties of light, thus making it possible to manipulate the velocity of light.

SLM was used to sculpt the spatio-temporal spectrum in an efficient manner and thus modify the group velocity. When the researchers manipulated the spatial and temporal degrees of freedom simultaneously, they found out that the group velocities were varying arbitrarily, sometimes more than the speed of light and sometimes less. They were also propagating in the forward direction away from the source and even travelling backward.
The mixing of the two main properties of light was essential to the success and scientists hope that these results can be used in a fruitful way in the future.


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