“…This means that to approach population inversion, using rhodamine 6G under visible laser excitation, pump intensities exceeding ∼5 × 10 23 photons cm −2 s −1 are necessary (see also Dienes and Yankelevich, 1998). This means that to approach population inversion, using rhodamine 6G under visible laser excitation, pump intensities exceeding ∼5 × 10 23 photons cm −2 s −1 are necessary (see also Dienes and Yankelevich, 1998).…”