Photonic crystals can bend light like gravity

A collaborative group of researchers has shown they can manipulate the behavior of light as if it were under the influence of gravity. Their findings, reported in a paper in Physical Review A, have far-reaching implications for the world of optics and materials science, and bear significance for the development of 6G communications.

Albert Einstein’s theory of relativity has long established that the trajectory of electromagnetic waves – including light and terahertz electromagnetic waves – can be deflected by gravitational fields.

Recently, scientists have theoretically predicted that the effects of gravity can be replicated (so-called pseudogravity) by deforming crystals in the lower normalized energy (or frequency) region. “We set out to explore whether lattice distortion in photonic crystals can produce pseudogravity effects,” says Kyoko Kitamura from Tohoku University’s Graduate School of Engineering in Japan.

Photonic crystals possess unique properties that allow scientists to manipulate and control the behavior of light, serving as ‘traffic controllers’ for light within crystals. They are constructed by periodically arranging two or more different materials with varying abilities to interact with and slow down light in a regular, repeating pattern. Furthermore, pseudogravity effects due to adiabatic changes have been observed in photonic crystals.

In this study, Kitamura and her colleagues modified photonic crystals by introducing lattice distortions: gradual deformations of the regular spacing of elements, which disrupted the grid-like pattern of the photonic crystals. This manipulated the photonic band structure of the crystals, resulting in a curved beam trajectory in-medium – just like a light-ray passing by a massive celestial body such as a black hole.

Specifically, the researchers employed a silicon-distorted photonic crystal with a primal lattice constant of 200µm and terahertz waves. In experiments, they successfully demonstrated the deflection of these waves.

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

“Such in-plane beam steering within the terahertz range could be harnessed in 6G communication,” said Masayuki Fujita, an associate professor from Osaka University in Japan. “Academically, the findings show that photonic crystals could harness gravitational effects, opening new pathways within the field of graviton physics.”

This story is adapted from material from Tohoku University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.