First Observation of the Cherenkov Radiation Phenomenon in a 2D Space

Researchers from the Andrew and Erna Viterbi Faculty of Computer and Electrical Engineering at the Technion– Israel Institute of Technology have shown the first experimental observation of Cherenkov radiation constrained in two measurements. The results are a new record in electron-radiation coupling strength, disclosing radiation quantum properties.

Cherenkov radiation is considered a unique physical phenomenon that has been used in medical imaging, particle discovery applications, and laser-driven electron accelerators for several years. The advancement attained by the Technion researchers links this phenomenon to future photonic quantum computing applications and free-electron quantum light sources.

The study released in Physical Review X was headed by Ph.D. students Shai Tsesses and Yuval Adiv from the Technion, together with Hao Hu from the Nanyang Technological University, Singapore. Today, a professor at Nanjing university in China. It was monitored by Prof. Ido Kaminer and Prof. Guy Bartal of the Technion in collaboration with colleagues from China: Prof. Hongsheng Chen and Prof. Xiao Lin from Zhejiang University.

The phenomenon

The interactions of free electrons with light underlie many known radiation phenomena and have led to various applications in science and industry. One of the most essential of these interaction impacts is the Cherenkov Radiation– electromagnetic radiation emitted when a charged particle, like an electron, travels through a medium at a speed greater than the phase velocity of light in that particular medium. It is the optical matching of a supersonic boom, which takes place, for instance, when a jet travels faster than the sound speed. As a result, Cherenkov radiation is occasionally called an “optical shock wave.” The phenomenon was discovered in 1934. In 1958, the scientists who found it were awarded the Nobel Prize in Physics.

Ever since, during greater than 80 years of research, the investigation of Cherenkov radiation caused the development of a wealth of applications, the majority of them for medical imaging and particle identification detectors. However, despite the intense fixation with the phenomenon, most theoretical research and all experimental demonstrations worried about Cherenkov radiation in the three-dimensional area and based its description on classical electromagnetism.

Now, the Technion researchers show the first experimental observation of 2D Cherenkov Radiation, demonstrating that in the two-dimensional area, radiation acts in a completely various manner– for the first time, the quantum description of light is necessary to explain the experimental results.

2D Cherenkov Radiation

The researchers engineered a unique multilayer structure enabling interaction between free electrons and light waves following a surface. The intelligent engineering of the structure permitted a first dimension of 2D Cherenkov Radiation. The reduced dimensionality of the effect allowed a glimpse into the quantum nature of the process of radiation discharge from free electrons: a count of the variety of photons (quantum particles of light) given off from a single electron and indirect evidence of the entanglement of the electrons with the light waves they produce.

In this context, “entanglement” implies a correlation between the properties of the electron and that of the light produced, such that measuring one provides information concerning the other. It is better to note that the 2022 Nobel Prize in Physics was granted for the performance of a series of experiments that demonstrate the results of quantum entanglement (in systems different from those demonstrated in the present research).

Yuval Adiv states, “The outcome of the research which surprised us the most worries the performance of electron radiation emission in the experiment: whereas the most sophisticated experiments that came before the present one attained a regime in which around just one electron out of one hundred produced Radiation, here, we succeeded in attaining an interaction routine in which every electron emitted Radiation. In other words, we could show an enhancement of over two orders of magnitude in the interaction performance (the coupling strength). This outcome aids the development of modern, efficient electron-driven radiation sources advancements.”

Prof. Kaminer’s explanation

Prof. Kaminer says, “Radiation released from electrons is an old phenomenon that has been investigated for over 100 years and was incorporated into the technology a long time back, an example being the home microwave. For several years, we had already discovered everything there was to learn about electron radiation, and the concept that this kind of radiation had already been totally described by classical physics became entrenched. In striking contrast to this concept, our experimental apparatus permits the quantum nature of electron radiation to be revealed”.

“The new experiment that was now released explores the quantum-photonic nature of electron radiation. The experiment belongs to a paradigm change in how we comprehend this radiation and, more broadly, the relationship between electrons as well as the radiation they emit. For instance, we now understand that free electrons can become entangled with the photons they release. It is both unusual and interesting to see indications of this phenomenon in the experiment.”

Shai Tsesses states, “In Yuval Adiv’s new experiment, we obliged the electrons to travel in proximity to a photonic-plasmonic surface planned based on a method created in the laboratory of Prof. Guy Bartal. The electron velocity was accurately set to acquire a huge combining strength, greater than that acquired in normal situations, where combining is to Radiation in three dimensions. At the heart of the process, we observe the spontaneous quantum nature of radiation emission, obtained in discrete packages of energy called photons. This way, the experiment sheds new light on photons’ quantum nature.”

Read the original article on PHYS.

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