Compiled by Photonics Spectra staff
BERKELEY, Calif. – Superlenses that are ideal for capturing light in the mid-infrared
range now can be fabricated more easily. Made from perovskite oxides rather than
metamaterials, these new devices could open the door to highly sensitive biomedical
detection and imaging.
It’s possible that the superlensing effect can be selectively
turned on and off, which would enable highly dense data writing and storage, researchers
at Lawrence Berkeley National Laboratory report.
With the ability to capture the evanescent lightwaves 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. However, their use has been limited
because most have been made from metamaterials, which can be difficult to fabricate
and tend to absorb a relatively high percentage of photons that otherwise would
be available for imaging.
Superlenses overcome the diffraction
limit by capturing the evanescent lightwaves, which carry detailed information about
object features that are significantly smaller than incident light wavelengths;
evanescent waves dissipate after a very short distance and seldom reach conventional
The scientists demonstrated a superlens for electric evanescent
fields with low absorption losses using perovskites in the mid-infrared regime.
Their spectral studies of lateral and vertical distributions of the evanescent waves
around the image plane of the lens showed that they had achieved an imaging resolution
of 1 μm, about 1/14 of the working wavelength, they said.
The perovskites they used to make their superlens, bismuth ferrite
and strontium titanate, feature a low rate of photon absorption and can be grown
as epitaxial multilayers whose highly crystalline quality reduces interface roughness
so there are few photons lost to scattering. The combination of low absorption and
scattering losses significantly improves the imaging resolution of the superlens.
Additionally, its ferroelectricity, piezoelectricity, superconductivity and magnetoresistance
could inspire new functionalities of perovskite-based superlenses, including nonvolatile
memory, microsensors, microactuators and nanoelectronics, the scientists said.
The research, published in the March 22, 2010, issue of Nature
Communications (doi: 10.1038/ncomms1249), represents the first application of perovskite
materials to superlensing.