Two-Color Superfluorescence of O 2 ` − Centers in KCl
R. Florian, L.O. Schwan, D. Schmid
If O 2 ` − centers in KCl are excited in their fundamental absorption band (at about 250 nm), they yield a fluorescnece spectrum which at low temperatures is dominated by a progression of very narrow zero-phonon lines (Δν1/2≈1cm−1) with a large Stokes shift (roughly 23000 cm−1 or 2.9 eV). At very high excitation intensities (≳ 20 GW/cm2) with single pulses of the fourth harmonic of a modelocked Nd-YAG laser (λ = 266 nm, pulse duration 30 ps, pulse energy ~ 100 μJ) and at low temepratures (T < 30 K) one observes a simultaneous coherent emission at the wavelength of two of the zero-phonon lines (0-10 and 0-11 transition at 594.77 and 629.14 nm, respectively) /1/, which can be identified as two-color superfluorescence fron a three-level system /2,3/.
International Conference on Luminescence - 1984•Jan 1, 1984•1 citation