Berkeley Lab Researchers Make First Perovskite-based Superlens For The İnfrared

Superlenses earned their superlative by being able to capture the "evanescent" light waves that blossom close to an illuminated surface and never travel far enough to be "seen" by a conventional lens. Superlenses hold enormous potential in a range of applications, depending upon the form of light they capture, but their use has been limited because most have been made from elaborate artificial constructs known as metamaterials. The unique optical properties of metamaterials, which include the ability to bend light backwards - a property known as negative refraction - arise from their structure rather than their chemical composition. However, metamaterials can be difficult to fabricate and tend to absorb a relatively high percentage of photons that would otherwise be available for imaging. Now, researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have fabricated a superlens from perovskite oxides that are simpler and easier to fabricate than metamaterials, and are ideal for capturing light in the mid-infrared range, which opens the door to highly sensitive biomedical detection and imaging. It is also possible that the superlensing effect can be selectively turned on/off, which would open the door to highly dense data writing and storage.

"We have demonstrated a superlens for electric evanescent fields with low absorption losses using perovskites in the mid-infrared regime," says Ramamoorthy Ramesh, a materials scientist with Berkeley Lab's Materials Sciences Division, who led this research. "Spectral studies of the lateral and vertical distributions of evanescent waves around the image plane of our lens show that we have achieved an imaging resolution of one micrometer, about one-fourteenth of the working wavelength."

Ramesh, who also holds appointments with the University of California Berkeley's Department of Materials Science and Engineering and the Department of Physics, is the senior author of a paper in the journal Nature Communications titled "Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling."

Conventional lenses create images by capturing the propagating light waves emitted by an object under illumination and then bending these captured light waves into focus. No matter how perfect a conventional lens is, the smallest image it can ever resolve is about half the wavelength of the illuminating (incident) light - a restriction known as the "diffraction limit." Superlenses overcome the diffraction limit by capturing the evanescent light waves, which carry detailed information about features on an object that are significantly smaller than the wavelengths of incident light. Because evanescent waves dissipate or "vanish" after traveling a very short distance, conventional lenses seldom ever see them.