Helium-Neon Lasers are gas lasers that use a mixture of helium and neon as its medium.  This is usually excited by a DC electrical discharge.  These lasers have many industrial and scientific uses.  In laboratory demonstrations, they are commonly used in the field of optics.  The Laserdisc players actually use a helium-neon laser to read the optical disk.  SCI Analytical provides a Helium-Neon Mixture for helium-neon lasers with 8.3% to 20% Neon with balance Helium.