In a laser printer, a laser is used to give individual “pixels” on a piece of paper a positive charge. Negatively charged toner particles stick to these positive regions, and a heat source then fuses the toner to the paper, extremetech.com reported.
In the laser unprinter, very short pulses of laser light — on the order of picoseconds (one millisecond contains one billion picoseconds) — are used to vaporize the toner. The trick is to do this without damaging the paper, which the team does by using green laser light that is readily absorbed by dark toner, but which passes harmlessly through cellulose fibers in paper.
