A team of applied physicists at the Harvard School of Engineering and Applied Sciences have recently created an ultra-thin lens that's capable of focusing light almost on the limits of the laws of diffraction.
At 60 nanometres thick, the lens is roughly 1000 times thinner than a human hair and essentially two-dimensional. It's made by plating a super-thin wafer of silicon with a nanometre-wide layer of gold. The gold is then stripped away to leave a pattern of v-shaped arrows on the silicon's surface.
Shine a laser onto the silicon-gold surface and the gold v-shaped arrows act as nanoantennae that capture the light, hold on to it briefly, and then release it again. By calibrating the length of the delay between capturing and releasing the light waves, the direction of the light can be changed: you have, then, a super-thin lens. A super-thin lens that doesn't suffer from optical aberrations, like the fish-eye effect. Whatever the signal it's detecting, the resulting image should be perfect and won't need to be corrected. Sure, sometimes we like the distortion that we get off of our wide angle lenses, but not all the time.
By changing the specific size, angle, and spacing of the nanoantennae, they can be tuned to particular wavelengths of light, too.
At the moment, these lenses are operating at wavelengths that we use for fibre-optic communication. But there's potential to use them to create flat microscope objectives.
As far as the lead author of the research paper, Francesco Aieta, is concerned, these flat lenses could entirely change the manufacture of optical products: 'In the future we can potentially replace all the bulk components in the majority of optical systems with just flat surfaces.'
And from then, perhaps the ultimate pancake lens?
With thanks to the Harvard School of Engineering and Applied Sciences, and my friend Colin.