A gas laser which is pumped using energy transfer from other atoms or molecules. Examples are the helium-neon (
HeNe) and the copper vapour laser.
Source:
PAC, 1995, 67, 1913. 'Nomenclature, symbols, units, and their usage in spectrochemical analysis-XV. Laser-based molecular spectroscopy for chemical analysis - laser fundamentals (IUPAC Recommendations 1995)' on page 1919 (https://doi.org/10.1351/pac199567111913)