Physicists break the speed of light with pulses inside hot plasma: ScienceAlert

Most of us grew up familiar with the prevailing law that limits the speed of information transmission through empty space: the speed of light, which is 300,000 kilometers (186,000 miles) per second.

While the photons themselves are unlikely to break this speed limit, there are features of light that do not operate by the same rules.

Manipulating them won’t speed up our ability to travel to the stars, but it could help us pave the way to a whole new class of laser technology.

Physicists in the United States have shown that under certain conditions, waves composed of groups of photons can move faster than light.

The researchers have been playing hard and fast with the maximum speed of light pulses for a while, speeding them up and even slowing them down to a hypothetical steady state using different materials like cold atomic gasesAnd the refracting crystalsAnd the Optical fiber.

But impressively, last year, researchers from Lawrence Livermore National Laboratory in California and the University of Rochester in New York swirled them inside hot swarms of charged particles, tuning the speed of light waves inside plasmas to anywhere from about a tenth of the light. Normal vacuum velocity to more than 30 percent faster.

This is more – and less – impressive than it sounds.

To break the hearts of those who hope it will lead us to Proxima Centauri and back in time for tea, this ultra-light travel falls within the laws of physics. Sorry.

The photon’s velocity is held in place by weaving electric and magnetic fields referred to as electromagnetism. It can’t get around that, but the photon pulses within narrow frequencies also jostle in ways that create regular waves.

The rhythmic rise and fall of entire groups of light waves move through objects at a rate described as group speeda “wave of waves” that can be modified to slow down or accelerate, depending on the electromagnetic conditions of its surroundings.

By stripping electrons from a stream of hydrogen and helium ions using a laser, the researchers were able to change the speed of the array of light pulses sent through it by a second light source, putting the brakes on or simplifying it by modulating the gas ratio and forcing the pulse features to change their shape.

The overall effect was due to the refraction from the plasma fields and the polarized light from the primary laser used to strip them. The individual light waves were still approaching their usual pace, even as their collective dance seemed to be accelerating.

From a theoretical point of view, the experiment helps model plasma physics and puts new limitations on the accuracy of existing models.

In practice, that’s good news for advanced tech waiting in the wings for clues on how to bypass the obstacles to making it a reality.

The lasers will be the big winner here, especially the insanely powerful variety. Old school lasers rely on solid-state optical materials, which tend to deteriorate with increased power. Use of plasma streams Amplifying or changing the properties of light would overcome this problem, but to get the most out of it we really need to model its electromagnetic properties.

It is no coincidence that Lawrence Livermore National Laboratory is keen to understand the optical nature of plasmas, being home to some of the most extensive laboratories in the world. Brilliant laser technology.

More powerful lasers are what we need for a full range of applications, from increasing particle accelerators to optimizing Clean Fusion Technology.

It may not help us move through space faster, but it is these very discoveries that will speed us toward the future we all dream of.

This research was published in physical review messages.

A version of this article was first published in May 2021.

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