Summary: A team of researchers from the Technion – Israel Institute of Technology has observed branched flow of light for the very first time. The findings are published in Nature and are featured on the cover of the July 2, 2020 issue.
Original author and publication date: American Technion Society – July 1, 2020
Futurizonte Editor’s Note: I am simply amazed that we are still seeing light for the first time. I can imagine that light still has many more secrets for us.
From the article:
The study was carried out by Ph.D. student Anatoly (Tolik) Patsyk, in collaboration with Miguel A. Bandres, who was a postdoctoral fellow at Technion when the project started and is now an Assistant Professor at CREOL, College of Optics and Photonics, University of Central Florida. The research was led by Technion President Professor Uri Sivan and Distinguished Professor Mordechai (Moti) Segev of the Technion’s Physics and Electrical Engineering Faculties, the Solid State Institute, and the Russell Berrie Nanotechnology Institute.
When waves travel through landscapes that contain disturbances, they naturally scatter, often in all directions. Scattering of light is a natural phenomenon, found in many places in nature. For example, scattering of light is the reason for the blue color of the sky. As it turns out, when the length over which disturbances vary is much larger than the wavelength, the wave scatters in an unusual fashion: it forms channels (branches) of enhanced intensity that continue to divide, or branch out, as the wave propagates. This phenomenon is known as branched flow. It was first observed in 2001 with electrons, and had been suggested to be ubiquitous and occur also for all waves in nature, for example sound waves and even ocean waves. Now, Technion researchers are bringing branched flow to the domain of light: they have made an experimental observation of branched flow of light.
“We always had the intention of finding something new, and we were eager to find it. It was not what we started looking for, but we kept looking and we found something far better,” said Asst. Prof. Miguel Bandres. “We are familiar with the fact that waves spread when they propagate in a homogeneous medium. But for other kinds of mediums, waves can behave in very different ways. When we have a disordered medium where the variations are smooth, like a landscape of mountains and valleys, the waves will propagate in a peculiar way. They will form channels that keep dividing as the wave propagates, forming a beautiful pattern resembling the branches of a tree.”
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 for light.
“In optics we usually work hard to make light stay focused and propagate as a collimated beam, but here the surprise is that the random structure of the soap film naturally caused the light to stay focused. It is another one of nature’s surprises,” said Tolik Patsyk.
The ability to create branched flow in the field of optics offers new and exciting opportunities for investigating and understanding this universal wave phenomenon.