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SciTech

This Pinay physicist can slow down light without touching it





Filipina physicist Dr. Jacquiline Romero and her colleagues at the University of Glasgow have managed to slow down light particles in a near-vacuum—something that's long been thought possible, but never proven experimentally until now.
 
Everyday optics
 
Although the maximum speed of light is a cosmological constant—made famous by Einstein's Special Theory of Relativity and E=mc2—it can, in fact, be slowed down: that's what optics do.
 
Every time you put on your eyeglasses or look into a fish bowl, you're actually slowing light down. This is because when light travels through a medium such as glass or water, its speed and direction change—a phenomenon we commonly know as "refraction".

Using various materials to control the speed of light is as old as history itself.
 
Just recently, scientists have even been able to use special materials to make light come to a complete stop: in 2013, German physicists successfully trapped photons inside a crystal for a full minute.
 
Slowing without touching
 
But the amazing thing about Dr. Romero's and her colleagues' work is that they've been able to slow down light without directly touching it.
 
Using special equipment, they were able to change the shape of photons traveling in empty space so that the light particles hit their target later than they normally would.
 
"The photons' transverse shape makes them travel a bit more slowly, at 0.001% slower than the (normal) speed of light," Dr. Romero told GMA News Online in an exclusive interview.
 
"You can think of these rays as passing through a lens, except that this is all happening in free space! The light isn't interacting with any material—like when it slows down while inside a glass of water, for example—but it's still traveling slower," she explained.
 
Dr. Romero said that it was the first time she is aware of that this theoretical effect has been reproduced in the laboratory.
 
"There's been previous experimental work on Bessel beams, but definitely nothing at the level of single photons—which does make (our) experiment really elegant and unambiguous," she told GMA News Online.

Suspending sunlight in thin air

So is it possible to make light come to a complete stop using these techniques?

It's theoretically possible, according to Dr. Romero, but beyond the capability of current technology.

"If you look at the theory, it's possible in principle, but it will be very hard. What it entails is really to have light energy confined almost just in the cross-section," she said.
 
While there are no immediate practical uses for this feat, it's undeniably romantic to imagine the possibility of suspending sunlight in thin air.
 
Proud Pinay
 
Dr. Romero is a graduate of the University of the Philippines and is currently a postdoctoral fellow studying quantum physics and information at the University of Glasgow.
 
She co-authored the paper, "Spatially structured photons that travel in free space slower than the speed of light" with fellow phsicists Daniel Giovannini, Václav Potocek, Gergely Ferenczi, Fiona Speirits, Stephen M. Barnett, Daniele Faccio, and Miles J. Padgett.
 
Some of Dr. Romero's essays have previously been featured in GMA News Online's Pinoy Abroad and SciTech sections. — GMA News
Tags: physics, light
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