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New Flat Lens Focuses Without Distortion
yahyamf writes "Applied physicists at Harvard have created an ultrathin, flat lens that focuses light without the distortions of conventional lenses. 'Our flat lens opens up a new type of technology,' says principal investigator Federico Capasso. 'We're presenting a new way of making lenses. 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. It's extremely exciting.'" And by "ultrathin," they mean it — 60 nanometers thin. The big advantage for this technology, aimed at telecommunications signals, is that "the flat lens eliminates optical aberrations such as the 'fish-eye' effect that results from conventional wide-angle lenses. Astigmatism and coma aberrations also do not occur with the flat lens, so the resulting image or signal is completely accurate and does not require any complex corrective techniques."
Have the cameraman back up, which lessens perspective distortion. When taking pictures of people you should always get as far back as possible and zoom in. Staying close and zooming out is bad.
My colleagues work on the exact same gold-based nano-antennae used by this work. All of the nano-antennae on the lens' surface are basically arranged to absorb and re-transmit the incoming light into a near perfect spot. Because it uses metal on nanoscopic scales to manipulate light in a way other than pure reflection (like a mirror), it's in the field of plasmonics. (Below a certain frequency [of light] the electrons in a metal react like a plasma, hence the name.)
Whenever us optical engineers hear about plasmonics, we internally roll our eyes, because metal almost always absorbs far too much light to be useful. Even tens of nanometers of penetration and/or propagation can extinguish almost all of the light. This essentially relegates the entire field to the realm of theoretical curiosities and nothing more. (This work uses 60nm thick gold)
The authors of this paper admit that absorption is their biggest obstacle, as this lens only passes 10% of the incoming light. There are other issues for making this work a reality, but they pale in comparison to the classic brick wall you get when passing light through metal.
AccountKiller
Reposting what I posted as AC up above on accident: Just to clarify: the demonstrated lens operates at 1.55 micron (near-IR). The same phase-control concept has already been demonstrated in the mid-IR by the same authors, in the terahertz (THz) by some other authors. The approach is trivially generalizable to any longer wavelength (shorter frequency) which means millimeter wave, radio waves, etc, though it is unclear if it is very useful in the radio frequency region compared to conventional receiving/transmitting phased arrays.
No, unfortunately the concept is not generalizable to gamma ray frequencies (or xrays). It involves plasmonic components, which require metals with plasma frequencies above the operating frequency (otherwise the metals stops acting as a metal). There is no metal which would still behave "metallic" at gamma ray frequencies, I believe.