Helium-Cadmium lasers can be categorized among either:

• Metal vapor lasers - Cadmium is a metal, the lasing action in Helium Cadmium laser occurs between energy levels of Cadmium ions, so the lasing medium is ionized metal vapor.
• Ion gas lasers - The properties of Helium-Cadmium laser are similar to those of Helium-Neon laser which is a neutral atom gas laser.

The excitation to the upper laser level of the Cadmium atoms in the gas is similar to the excitation process of the Neon gas in a Helium-Neon laser: Helium atoms are excited by collisions with accelerated electrons, and than they pass their energies to Cadmium atoms by collisions.

The transitions in Helium-Cadmium laser are between energy levels of singly ionized Cadmium atoms, and about twelve lines are available. These wavelengths are in the shorter wavelength region, violet and Ultra-Violet (UV). Thus, the main application of the He-Cd laser is in the optics laboratory, for fabricating holographic gratings.

The practical problem in Helium-Cadmium laser is to maintain homogeneous distribution of the metal vapor inside the electrical discharge tube. The ions are attracted to the cold windows at the ends of the cavity. In order to prevent coating of the windows with Cadmium, cold traps are put before the laser windows.