“Pseudogravity” in crystals bends light much like gravitational lenses
We probably won’t just make a cosmic gravitational lens. But physicists can produce pseudogravity, when a photonic crystal with a disturbed structure changes the path of light rays, similar to the gravity of space monsters. It can be an interesting experimental tool as well as a practical application.
Gravity can do wonders with light. Credit: NASA’s Goddard Space Flight Center/Jeremy Schnittman.
It follows from the general theory of relativity that gravity bends space-time and thus also the path of light rays that fly through this space-time. It has wondrous consequences, for example in the form of gravitational lensing, where the mammoth gravitational influence of cosmic objects magnifies the images of other objects we observe far beyond.
On the left, a deformed photonic crystal. Credit: Nanjyo et al. (2023), Physical Review A.
Our civilization will probably have to wait a little longer before making a cosmic gravitational lens. Physicists have recently discovered a way to imitate this phenomenon in photonic crystals.
These structures are used in various optical devices and experiments. They are usually made of materials that are arranged in periodic patterns.
Pseudogravity experiments. Credit: Nanjyo et al. (2023), Physical Review A.
Earlier theoretical studies predicted that photonic crystals with a spatially disordered structure should change the path of electromagnetic radiation much like cosmic gravitational lenses. This is called pseudogravity.
A Japanese team of experts, led by Kyoko Kitamura from Tohoku University, tested pseudogravity in an experiment. They created a photonic crystal from silicon, which they disrupted the structure of so that it was deformed in a suitable way. Then they shined terahertz radiation on the photonic crystal.
The experiment was designed so that if pseudogravity didn’t work, the beam of radiation would go out against the entrance.
The kind reader must have already guessed that the terahertz beam was diverted from its path and detected by the lucky Japanese team. According to Kitamura et al. this could make an interesting method for manipulating light beams in optical systems and other similar devices.
Since this is terahertz radiation, pseudogravity could be applied in the developing 6G technologies. It could also be a goldmine for physicists studying the elusive gravity.
Video: Photonic Crystals
Literature
Physical Review A 108: 033522.
2023-10-18 20:42:33
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