Gravitational lensing re-created using metamaterials

Nature : Gravitational lensing is an optical effect caused by the curvature of spacetime around large masses that lie between a light source and an observer. The curvature causes the light source to appear to the observer to be in a different location than it actually is. The phenomenon was originally predicted by Einstein’s general theory of relativity and later verified by astronomers. Now the effect has been re-created in a laboratory by Hui Liu of Nanjing University in China and his colleagues. But instead of light being bent by the gravity of spacetime, it was bent due to the index of refraction of certain metamaterials applied to an integrated photonic chip. The researchers sent laser light through a clear layer of plastic on the chip to which they had added polystyrene microbeads, which varied the thickness and index of refraction of the plastic. The result was that the laser light bent continuously as it passed through the plastic instead of just at the transition point between air and plastic. Having an optical analogue for lensing provides controllable conditions under which it may be easier to study its effect.