The laser printer has in a few years become the dominant mode of printing in offices. It employs a semiconductor laser and the xerography principle. The laser is focused and scanned across a photoactive selenium coated drum where it produces a charge pattern which mirrors the material to be printed. This drum then holds the particles of the toner to transfer to paper which is rolled over the drum in the presence of heat. The typical laser for this application is the aluminum-gallium-arsenide (AlGaAs) laser at 760 nm wavelength, just into the infrared.
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