brightness

of a laser dye
Product of the fluorescence quantum yield (Φ f) of a dye and the molar decadic absorption coefficient at the excitation wavelength, ɛ λ, i.e., Φ f ɛ λ.
Source:
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 310