Recently, the researchers succeeded in causing the two laser pointer beams to interfere with each other and eventually wrap around each other, like knotted laces or knots on a sailboat.
Researchers point out that "knots" are not necessarily made of rope, but can be mathematical terms of any shape that wraps around in a particular way in space. By using the complex shapes formed by the light waves moving in two directions (up and down and left and right) along the way, and the interaction of the light waves, they can cause the electromagnetic field to be knotted in the air.
The "knot" mentioned here is very clear in the light wave data image, and the 8-word knot and the torus knot can be recognized. The researchers also used formal knot theory mathematics to confirm their findings.
To create these "knots," the researchers carefully adjusted the up and down and left and right fluctuations (polarization) of the two beams of the laser pointer, using the same technology as polarized sunglasses. The "knot" is formed at the "polarized singularity" - the singularity of the polarization is the intersection of the two beams, that is, where the left and right wavelengths are equal, surrounded by light of many other wavelengths. At these points, light bends in the way the researchers want.
“We can all skillfully tie tangible materials such as laces or ribbons,” says Mark Dennis, a physicist at the University of Bristol. “But it’s more complicated to tie the light into a knot. It’s not just about a bunch of lines. The light of the shape also involves the space of light propagation or the 'field'."
The researchers hope to turn the light into a more complex knot later, hoping that this technology will accelerate the development of a more precisely tuned laser pointer source. Relevant research results have been published in the journal Nature Physics.