  Stimulated amplification of fluorescence signals is obtained under conditions
which approach biocompatibility by adding NanoParticles (NPs) to an aqueous
solution of fluorescein. The conditions for the stability of the suspension and
optimum dye concentration are detailed, together with considerations on
photobleaching and phototoxicity. A dedicated experimental setup, coupled to a
specified measurement protocol, prove that it is possible to obtain gain
factors up to 40, with a considerable reduction in spectral fluorescence
linewidth. A pump-energy- and NP-concentration dependence of the fluorescence
pulse duration is interpreted as further proof of stimulated amplification.
Perspectives and possible biological applications are discussed.
