Microvision's current pico projection engine uses red and blue laser diodes and a frequency-doubled "synthetic" green laser to create a full color image.

ENGADGET: Microvision integrates direct green laser into pico projector prototype, completes RGB achievement

By tuning the laser very precisely to the frequency of one particular sort of bond (such as that with a heavy carbon atom at one end), a molecule containing that bond can be shaken up.

ECONOMIST: Diamonds

And, just as light waves of the same frequency can be made to resonate in step with one another and so form a laser beam, it should be possible to make atoms of the same element resonate similarly.

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The laser beam in the scanner shoots a steady stream of photons, all of the same frequency, at the plastic.

ECONOMIST: Recycling