Which one of the following laser types is used in a laser printer?

Correct answer: 3) Semiconductor laser. Modern laser printers use compact semiconductor lasers (laser diodes) to produce the focused, scanned beam that writes the latent image on the photoconductor drum; laser diodes are widely used in laser printers, scanners and barcode readers. Other laser types listed are typically used for different purposes: gas lasers (e.g., CO2, He–Ne) serve cutting or pointing roles, excimer lasers are used for ultraviolet processing, and dye lasers are tunable laboratory sources rather than printer light sources. Because desktop and office printers require small, efficient, low-cost light sources, the semiconductor (laser diode) is the appropriate and commonly employed type.