active medium

https://doi.org/10.1351/goldbook.A00106
See:
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 1915 [Terms] [Paper]