Researchers at the Technion presented for the first time in the world an observation of the branching of light rays

The groundbreaking scientific discovery, achieved by projecting a laser beam onto the membrane of a soap bubble, opens up a new field in optics - Branched Flow of Light - and paves the way for new avenues of research in optics and opto-fluidics. The study was published on the cover of the prestigious scientific magazine Nature

Researchers from the Technion demonstrated for the first time an experimental observation of the branching of light rays. The findings were published this evening on the cover of the prestigious scientific journal Nature. The groundbreaking research was conducted by doctoral student Anatoly (Tulik) Petzuk and Dr. Miguel Banderas, who was a postdoctoral student at the Technion and is now a faculty member at CREOL, the Research Institute for Optics and Photonics at UCF, under the guidance of Technion President Prof. Uri Sion and Research Prof. Moti Segev from the Faculties of Physics and Electrical Engineering.

When waves pass through a medium that has disturbances - an inhomogeneous medium - they scatter, and sometimes scatter in all directions. The scattering of light is a natural phenomenon that occurs in many places in nature and is, for example, the reason why the sky appears blue to us.

It turns out that when the aforementioned disturbances change over distances greater than the wavelength, a very unique dispersion pattern is created: the light creates channels (branches) of increased intensities, and these channels continue to branch again and again as the wave progresses. This phenomenon was observed for the first time in the movement of electrons as early as 2001, and was called "Branched Flow" (Branched Flow). Following that discovery, it was hypothesized that branched flow would also exist in other types of waves in nature, including sound waves and even sea waves. Technion researchers have now discovered the said phenomenon in the world of optics, and through the experiments in optics, new features of the phenomenon and completely new ideas have been discovered.

"The branched flow of light was not the phenomenon we were looking for in the first place," says Prof. Miguel Banderas. "The goal of the research was to shape laser beams in a medium that is a curved space - a thin spherical shell. The thinnest shell we know is a soap bubble, so we launched laser beams into the molecular shell of a soap bubble. But when we managed to create a soap bubble stable enough so that the laser light could be sent into it - we discovered to our surprise that the light branches out inside the shell again and again like branches and sub-branches growing from a tree." It took a year before we realized that the branching is due to small changes in the thickness of the shell, which varies from point to point. In a normal situation, such changes scatter the light in all directions, but it turns out that when these "thickness disturbances" are not completely random - but have a characteristic size (like mountains and ravines) - the light is scattered from them by creating branches.

In their study, the researchers projected a laser beam onto a thin soap film whose thickness varies randomly. They discovered that when the light moves inside the crust it forms long branches - branched flow. According to doctoral student Tolik Petzuk, "In optics we usually work hard to allow light to move as a narrow and focused beam of light, but here we were surprised to discover that the random structure of the soap film focused the light itself and created an image reminiscent of the branches of a tree. Nature gives us surprises, and this is one of them."

"The success in demonstrating the phenomenon of a branched flow of light in optics opens up new ways of investigating and understanding wave phenomena," says Prof. Uri Sion, president of the Technion, faculty member of the Faculty of Physics and holder of the Bartoldo Badler Chair, "nothing is more exciting than the discovery of a new phenomenon in nature, and this is the first demonstration of the said phenomenon in light waves. It turns out that when nature smiles you can discover fascinating phenomena in very simple systems, and for that we just have to be attentive enough. Here was a joint effort of researchers from different fields, with different views and different backgrounds, which led to fascinating discoveries."

"The success in observing a branched flow of light opens up new possibilities in research, starting with the characterization of the medium in which the light progresses with great precision and ending with the precise tracking of these branches and the study of their properties," added Prof. Sion.

"Here is a scientific discovery published on the cover of Nature magazine due to the fact that it opens up a new field in optics, even though it currently has no immediate applications," said research professor Moti Segev, holder of the Dr. Bob Shilman Chair and member of the Israel National Academy of Sciences. "The story of this discovery is very interesting - the student Tolik was looking for one thing and discovered a completely different phenomenon, and instead of ignoring it and continuing the initial search, he asked himself, and us, what is going on here. This is how I teach my students to work - to always observe the experimental facts as they are and not to ignore phenomena that we see and find difficult to explain. Tolik and Miguel managed to significantly improve the experimental system, learned to stabilize the soap bubbles so that they did not explode despite the optical fiber piercing them (through which the light is introduced into the bubble), to a level that made it possible to isolate the physics at work here. It took us another whole year to understand that we are actually seeing a branched flow of light (Branched Flow of Light), a phenomenon that has never been studied in the context of light waves."

According to Research Prof. Segev, "Following this observation, we can think of many new directions. For example, controlling the branching of light to control currents in a liquid, or combining soap and a fluorescent substance to turn the branches into tiny laser sources, or using the soap membrane as a platform to study wave behavior. This groundbreaking research can lead to diverse follow-up studies in many fields, and as we have done many times in the past, even now we strive to explore and go to areas that no one has yet visited."

The research project is currently ongoing in the labs of Research Prof. Segev and Prof. Sion at the Technion, and at the same time in the new lab of Prof. Miguel Banderas at UCF. The research was conducted at the Solid State Institute in collaboration with the Russell Berry Research Institute in Nanotechnology (RBNI) at the Technion.
For the scientific article in Nature

More of the topic in Hayadan:
A photon and an electron meet inside a photonic crystal
Will XNUMXD glass printing make it possible to produce dynamic structures like in nature?
Semiconductor lasers: the next generation