Ultrathin wafer of silicon and gold focuses telecom wavelengths without distortion
August 27, 2012
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Applied physicists at the Harvard School of Engineering and Applied Sciences (SEAS) have created an ultrathin, flat lens that focuses light without imparting the distortions of conventional lenses.
Left:
A micrograph of the flat lens (diameter approximately 1 mm) made of
silicon. The surface is coated with concentric rings of gold optical
nanoantennas (inset) which impart different delays to the light
traversing the lens. Right:The colored rings show the magnitude of the
phase delay corresponding to each ring. (Credit: Francesco Aieta)
At a mere 60 nanometers thick, the flat lens is essentially two-dimensional, yet its focusing power approaches the ultimate physical limit set by the laws of diffraction.
Operating at telecom wavelengths (from near-infrared to up to terahertz wavelengths, the range commonly used in fiber-optic communications — but not visible light), the new device is completely scalable and simple to manufacture.
“We’re presenting a new way of making lenses,” says principal investigator Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS.
“Instead of creating phase delays as light propagates through the thickness of the material, you can create an instantaneous phase shift right at the surface of the lens.”
New York, US: United Nations’ member states and several international
organisations congregated here for the Second Session of the United
Nations Committee of Experts on Global Geospatial Information Management
(GGIM). The high level forum plays a leading role in setting the agenda
for the development of global geospatial information and to promote its
use to address key global challenges. 
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