Helium-Neon (HeNe) gas lasers were the first lasers mass-produced. They were used in everything from UPC scanners to video disc players and laser printers. Although they have been largely replaced by diode lasers, HeNe lasers still offer superior beam quality. A HeNe laser has a Gaussian irradiance profile and long coherence length. These beam characteristics are highly desirable in many laser applications including interferometry and holography.
