Flat lens - is this the breakthrough it seems to be?

Started Aug 12, 2013 | Discussions thread
jayrandomer
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The key quote
In reply to alanr0, Aug 12, 2013

alanr0 wrote:

meanwhile wrote:

Could this be the product to finally disproves the whole "you can't beat physics" argument to lenses needing to be a particular size?

https://www.seas.harvard.edu/news/2012/08/flat-lens-offers-perfect-image

As discussed previously, physics still applies, and the technology is not quite ready for mainstream photographic applications. As far as I can tell, the lens described is around 42 mm focal length, but only 1 mm diameter (so f:42). As others have stated, it only works for a narrow band of wavelengths, and the silicon substrate will be opaque to visible light.

They have simulation results suggesting the technique can be applied to high numerical aperture microscope objectives. However, it may be difficult to maintain low aberrations and high diffraction efficiency over a sufficiently wide field of view for more general purpose photography.

Cheers.

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Alan Robinson

“Our flat lens opens up a new type of technology,” says principal investigatorFederico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS. “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.”

That's the interesting part of the work.  As mentioned above its applicability to photography isn't immediate or technically feasible yet, in large part because the phase delay mechanism (little metal resonators) is extremely wavelength dependent.  The intended application (at the end of communication fibers) is much less demanding than imaging, though, so it's a very neat solution.

I think the real issue with optical wavelengths isn't the substrate (I'm sure glass or sapphire wafers could be substituted with some work) but rather the fabrication--visible wavelengths probably require pattern sizes smaller than what they can reliable generate.  The article mentions scaling from the near-infrared to the Terahertz, suggesting visible wavelengths are probably (at least for now) out of reach.

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