What primarily determines the name of a laser?

The name of a laser is primarily determined by the active medium used to generate the laser light. The active medium can be a gas, liquid, or solid that is energized to produce a population inversion, allowing for stimulated emission of radiation. Each type of active medium imparts specific properties to the laser, including its wavelength (color of the emitted light), efficiency, and operational characteristics. For example, a helium-neon laser is named after its gaseous active medium, which influences its operating wavelength and other properties.

The color of the laser light, while important, is a consequence of the active medium rather than a defining factor in the naming. Similarly, the power output refers to the intensity or energy delivered by the laser, and the application type describes what the laser can be used for but does not influence its name directly. Thus, the correct choice focuses on the fundamental aspect of how lasers are classified and named based on the properties and characteristics of their active mediums.