Physicists Tie Beam of Light into Knots

By Nancy Atkinson - January 18, 2010 at 10:23 AM UTC | Physics
Knot1lowres.jpg

[/caption] Imagine taking a beam of light and tying it in knots like a piece of string. Hard to fathom? Well, a group of physicists from the UK have achieved this remarkable feat, and they say understanding how to control light in this way has important implications for laser technology used in wide a range of industries.

"In a light beam, the flow of light through space is similar to water flowing in a river," said Dr. Mark Dennis from the University of Bristol and lead author of a paper published in

Nature Physics

this week. "Although it often flows in a straight line – out of a torch, laser pointer, etc – light can also flow in whirls and eddies, forming lines in space called 'optical vortices.' Along these lines, or optical vortices, the intensity of the light is zero (black). The light all around us is filled with these dark lines, even though we can't see them."

Optical vortices can be created with holograms which direct the flow of light. In this work, the team designed holograms using knot theory – a branch of abstract mathematics inspired by knots that occur in shoelaces and rope. Using these specially designed holograms they were able to create knots in optical vortices.

This new research demonstrates a physical application for a branch of mathematics previously considered completely abstract.

"The sophisticated hologram design required for the experimental demonstration of the knotted light shows advanced optical control, which undoubtedly can be used in future laser devices," said Miles Padgett from Glasgow University, who led the experiments

"The study of knotted vortices was initiated by Lord Kelvin back in 1867 in his quest for an explanation of atoms," addeds Dennis, who began to study knotted optical vortices with Professor Sir Michael Berry at Bristol University in 2000. "This work opens a new chapter in that history."

Paper: Isolated optical vortex knots by Mark R. Dennis, Robert P. King, Barry Jack, Kevin O'Holleran and Miles J. Padgett.

Nature Physics,

published online 17 January 2010.

Source:

University of Bristol

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com