Tag Archives: photonics

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Designing space telescopes the size of a dinner plate

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Could Future Telescopes Do Without the Mirror?

Tomorrow’s Hubble might be the size of a dinner plate.

For Air & Space Magazine:

Today’s telescopes can see better and farther than ever, but they have become expensive: NASA’s Kepler spacecraft, which discovered planets orbiting far-away stars, and the Large Synoptic Survey Telescope nearing completion in Chile, for example, each cost about half a billion dollars.

Researchers at Lockheed Martin have a radical proposal: Build the observatory without the telescope—sort of. The idea, called Segmented Planar Imaging Detector for Electro-optical Reconnaissance, or SPIDER, begins with large arrays of silicon chips called photonic integrated circuits (PICs). Each chip in SPIDER takes a wide-open image, like a mirror with no focusing point. Then a computer combines the images, gradually eliminating the blurring, in a method called interferometry. By the time thousands of PICs are combined, the image should be as sharp as one produced by a large—and expensive—telescope mirror.

[Read the rest at Air & Space Magazine…]

Aside by

(In honor of Terry Pratchett, I almost wrote that “Twisted light? Onna chip?”, but that would probably confuse 90% of my readers.)

Light is used to carry data, but mostly we don’t use the properties of the photons themselves to convey information. Quantum communication, among other applications, could use the state of the photon to encode data. In particular, the orbital angular momentum (OAM) state of a photon, where the photon describes a helix as it travels, can carry a lot of bits. Now researchers have fabricated a silicon chip to make twisted light.

Photons possess a number of quantum properties that can be used to encode information. You can think of photon polarization as like the rotation of a planet on its axis. In this view, the helical shape of the light wave—known as its orbital angular momentum (OAM)—is akin to the planet’s orbit around the Sun. These properties are independent of each other, and of the wavelength of light, so they can be manipulated separately. Whereas polarization occurs as a combination of two possible orientations, the OAM theoretically can have infinite values, though in practice far fewer states are available. Nevertheless, exploiting OAM greatly expands the potentially exploitable quantum states of photons we could put to use.

The researchers created helical OAM states using a ring-shaped chamber fabricated from silicon and mounted on a chip. [Read more….]

Twisted light on a silicon chip