Distorted crystals use ‘pseudogravity’ to bend light like black holes do

A new crystal can bend light like a black hole would, causing the light to bow away from its usual straight path.

This phenomenon, called pseudogravity, could be used in 6G communication technology, according to the authors of the new study, published Sept. 28 in the journal Physical Review A. This next-generation communication would transmit information wirelessly at ultrahigh speeds. Because the crystal mimics what happens when light passes by black holes and other ultradense space objects, the new technique could also be used to study so-called quantum gravity, a theory that would unite quantum mechanics and Albert Einstein’s theory of relativity.

According to relativity, light and other electromagnetic waves can be influenced by gravitational forces. This is called gravitational lensing, and astronomers use it all the time to study massive space objects such as quasars. Recreating such an effect in a laboratory environment is difficult, given the need for a huge amount of mass, but scientists have long suspected they could mimic the phenomenon using crystalline materials.

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To do so, Kyoko Kitamura, a professor in the graduate school of engineering at Tohoku University in Japan, and her colleagues started with photonic crystals, which are crystals of two or more arrangements that are arrayed in a regular, grid-like pattern and are capable of slowing light as it passes through them. The team gradually distorted these crystals, disrupting the crystalline lattice, and then shined beams of light through the crystals and watched them deflect.

“Much like gravity bends the trajectory of objects, we came up with a means to bend light within certain materials,” Kitamura said in a statement.

Manipulating light in this way is one potential pathway for next-generation communications technology, which will require sending information in the terahertz range, or above 100 gigahertz. (5G technology maxes out at 71 gigahertz.) Researchers believe that creative manipulation of light is one way to reach these frequencies. The new material could also have applications in research.

“Academically, the findings show that photonic crystals could harness gravitational effects, opening new pathways within the field of graviton physics,” study co-author Masayuki Fujita, an associate professor at Osaka University in Japan, said in the statement.

A graviton is the hypothetical quantum particle that mediates the force of gravity. No such particle has been observed yet, nor have scientists entirely worked out what this particle would even look like in theory.