RAMIFICATIONS OF LIGHT – PRESIDENT’S REPORT 2020

For the first time in history, human eyes watch how light branches in the flow.

Observation of branched flow of light - a laser beam propagating in a soap bubble. The channels keep dividing as the wave propagates, forming a beautiful pattern resembling the branches of a tree. The researchers are affiliated with the Russell Berrie Nanotechnology Institute. — Observation of branched flow of light – a laser beam propagating in a soap bubble. The channels keep dividing as the wave propagates, forming a beautiful pattern resembling the branches of a tree. The researchers are affiliated with the Russell Berrie Nanotechnology Institute.

A paradigm shift in optics and optofluidics occurred at Technion in 2020, as a game changing team in the Solid State Institute is awakening the world to the intimate workings of light.

Distinguished Prof. Mordechai (Moti) Segev, Technion President Prof. Uri Sivan, doctoral student Anatoly (Tolik) Patsyk and then-postdoctoral researcher Dr. Miguel Bandres were exploring the notion of branched flow, which was first observed in electrons in 2001. The suspicion was that this phenomenon could be common to all natural waves, including sound or even ocean waves.

Now, Technion scientists have documented the branched flow of light directly through laboratory observation. The revelations won the cover of the July 2, 2020 issue of the prestigious scientific journal Nature.

(l-r) Distinguished Prof. Moti Segev, Tolik Patsyk, Technion President Prof. Uri Sivan and Prof. Miguel Bandres.

In their research, the team coupled a laser beam to a soap membrane, which contains random variations in membrane thickness. They discovered that when light propagates within the soap film, rather than being scattered, the light forms elongated branches, creating the branched flow phenomenon.

“The random structure of the soap film naturally caused the light to stay focused. It is another one of nature’s surprises,” explained Patsyk.

Thin liquid membranes as a platform for observing branched flow of light.

“The fact that we observe it with light waves opens remarkable new possibilities for research. It gives us the ability to characterize the medium in which light propagates to very high precision and allows us to follow those branches accurately and study their properties,” said Sivan.

“We can think of a plethora of new ideas,” adds Segev, the Robert J. Shillman Distinguished Professor of Physics and Electrical Engineering. “For example, using these light branches to control the fluidic flow in liquid, or to combine the soap with fluorescent material and cause the branches to become little lasers. As we did many times in the past, we would like to boldly go where no one has gone before.”

The project is still in full branching flow in the laboratories of Profs. Segev and Sivan at Technion, in parallel in the newly established lab of Prof. Miguel Bandres at CREOL, College of Optics and Photonics, University of Central Florida.