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Curved lenses, like those in cameras or telescopes, are stacked in order to reduce distortions and resolve a clear image. That's why high-power microscopes are so big and telephoto lenses so long.
While lens technology has come a long way, it is still difficult to make a compact and thin lens (rub a finger over the back of a cellphone and you'll get a sense of how difficult). But what if you could replace those stacks with a single flat -- or planar -- lens?
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have demonstrated the first planar lens that works with high efficiency within the visible spectrum of light -- covering the whole range of colors from red to blue. The lens can resolve nanoscale features separated by distances smaller than the wavelength of light. It uses an ultrathin array of tiny waveguides, known as a metasurface, which bends light as it passes through, similar to a curved lens.
The article's description of the lens sounds reminiscent of a Fresnel lens. Perhaps Soylentils more familiar with the field can comment?
(Score: 2) by Fnord666 on Sunday June 05 2016, @06:43PM
The lens in this article is completely different: metamaterials are fabricated on a nano-scale, and work by way of interferometric interactions between the light's wavefront (phase front) and the structure of the nanomaterial. A classic lens, including Fresnell, works due to the difference in index of refraction between air and glass, and Snell's law thereof.
(and yes, I am an optical physicist)
Question for you. Some of the discussion of this lens seemed to indicate that the lens only worked for one wavelength of light. To work on a different wavelength the nanostructures would have to be reorganized. Is that correct?
(Score: 2) by cellocgw on Sunday June 05 2016, @07:56PM
Yes, that's my impression as well (that the current design is monochromatic). From what little I know of current metamaterial designs, the physical spacing of the layout only fits one wavelength. There's always some "bandwidth" the same way an FM receiver can handle a signal thats slightly off-center frequency, but that's about it.
Physicist, cellist, former OTTer (1190) resume: https://app.box.com/witthoftresume
(Score: 2) by Fnord666 on Monday June 06 2016, @02:45PM