Filipino Scientist Dr. Jacquiline Romero et al. Slows Down The Speed of Light

Filipino Scientist Dr. Jacquiline Romero was one of the scientists who made light travel slower than the speed of light. The speed of light has been known to be 299,792,458 meter per second (186,282 miles per second) in free space. But researchers from the University of Glasgow and Heriot-Watt University has shown that particles of light, known as photons, can be slowed as they travel through free space.

The results of the study titled ‘Spatially Structured Photons that Travel in Free Space Slower than the Speed of Light‘ can be found in the journal Science Express. It is also available here in PDF.

They sent photons through a special mask that changed the photons’ shape and made them travel to a slower speed.

The laboratory experiment was configured like a time trial race, with two photons released simultaneously across identical distances towards a defined finish line. The delay is several microns over a propagation distance of the order of 1 meter.

In an interview by BBC, Dr. Jacqui Romero explained, “After the mask, the photon is launched into a sort of racetrack about a meter in length. Then we take the time in which the unshaped photon finishes the racetrack, and the shaped photon’s time as well, and then compare the two times.”

Professor Miles Padgett, one of the scientists involved in the study from the University of Glasgow’s Optics Group, said that the crucial component of the study was the mask – a software controlled liquid crystal device: “That mask looks a little bit like a bull’s-eye target.”

“And that mask patterns the light beam, and we show that it’s the patterning of the light beam that slows it down. But once that pattern has been imposed – even now the light is no longer in the mask, it’s just propagating in free space – the speed is still slow.”

“The results give us a new way to think about the properties of light and we’re keen to continue exploring the potential of this discovery in future applications. We expect that the effect will be applicable to any wave theory, so a similar slowing could well be created in sound waves, for example,” Dr. Padgett added.

Dr. Greg Gbur, an optical physicist at the University of North Carolina at Charlotte, told Science News that the findings won’t change the way physicists look at the aura emanating from a lamp or flashlight. But he says the speed corrections could be important for physicists studying extremely short light pulses.

Who is Dr. Jacquiline Romero
Jacqui finished both her B.Sc. Applied Physics (2005) and M.Sc. Physics (2007) degrees in the University of the Philippines. In 2008, she was awarded a Synergy Studentship from the Universities of Glasgow and Strathclyde. She finished her Ph.D. in 2012 under the joint supervision of Prof. Miles Padgett and Prof. Steve Barnett. Jacqui’s research interests are in fundamental quantum physics explored via optical orbital angular momentum, high-dimensional entanglement and quantum information. She is currently a research associate in the University of Glasgow.

Full reference: Spatially structured photons that travel in free space slower than the speed of light, Science, DOI: 10.1126/science.aaa3035

ABSTRACT
That the speed of light in free space is constant is a cornerstone of modern physics. However, light beams have finite transverse size, which leads to a modification of their wavevectors resulting in a change to their phase and group velocities. We study the group velocity of single photons by measuring a change in their arrival time that results from changing the beam’s transverse spatial structure. Using time-correlated photon pairs we show a reduction of the group velocity of photons in both a Bessel beam and photons in a focused Gaussian beam. In both cases, the delay is several micrometers over a propagation distance of the order of 1 m. Our work highlights that, even in free space, the invariance of the speed of light only applies to plane waves.