A joint research team, comprising Associate Professor Shin-ichi Wada and Graduate Student Hiroyuki Ohta of the Graduate School of Advanced Science and Engineering at Hiroshima University, Specially Appointed Professor Masahiro Katoh of the Hiroshima Synchrotron Radiation Center at the same university, the Technical Center of Nagoya University, and the Nagoya University Synchrotron Radiation Research Center has announced the demonstration of a special type of light, known as an optical vortex, through Young's double-slit interference experiment using the synchrotron radiation source, UVSORIII, at the UVSOR Synchrotron Facility of the Institute for Molecular Science. This type of light, which travels in the form of spontaneous light whirlpools emitted by high-energy electrons, was demonstrated to exhibit vortex properties even in each individual particle (photon) that constitutes it. The results were published in Scientific Reports, an international academic journal, on December 27, 2023.
Provided by Hiroshima University
When light waves spread in a three-dimensional space, the ripples can be captured by the spread of a surface called a wavefront. This surface is called a spherical wave because it is a surface of a sphere. When the source of the waves is very distant, the wavefronts can be approximated as plane waves, and are referred to as plane waves. Unlike these waves, it is also known that a special type of light (optical vortex) exhibits a spiral wavefront.
The existence of optical vortices was theoretically demonstrated in 1992; subsequently, their experimental generation became possible. In this study, the research team focused on the light generated by electrons in a high-speed helical motion as they pass through a helical undulator. This helical undulator (synchrotron radiation generator) has a row of magnets arranged so that horizontal and vertical meandering motions of electrons were generated by which spiral motions of electrons can occur. The light emitted from these electrons contains a component in which the helical motion of the electrons is transferred as an optical vortex.
Young's double-slit interference experiment was conducted to investigate the fact that each photon resulting from the motion of a single electron also has vortex properties. British physicist Young's experiment demonstrated the wave nature of light by simultaneously illuminating light with aligned waves through two narrow slits; further, interference patterns of light and dark bands occur beyond them. The radiation emitted by electrons passing through this undulator was selectively extracted by the wavelength filter based on their wavelength to isolate components with optical vortex properties. Subsequently, the conditions where the photons one by one pass through the double-slit by means of a neutral density filter were created. The interference patterns were captured by a high-speed camera.
By accumulating individually captured images, the formation of interference stripes was observed. Distinct to the photon vortex, a dark and distorted stripe pattern emerged in the central part. These results indicate that each photon spontaneously emitted from a helical high-energy electron can have intrinsic spiral wavefront properties.
Wada stated that "Light is familiar to us and has been studied for a long time. Nevertheless, with the advancement of science and technology, new aspects of light continue to be explored even today. One such example is the attosecond pulses of light, which gained attention in last year's Nobel Prize in Physics. Additionally, the phenomenon of 'optical vortex' in this study has become achievable relatively recently. Various studies are being undertaken to explore the potential utility of this unique light phenomenon, along with the types of benefits it may bring to us. We are really interested in its future progress."
Journal Information
Publication: Scientific Reports
Title: Young's double-slit experiment with undulator vortex radiation in the photon-counting regime
DOI: 10.1038/s41598-023-49825-4
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.