Excition Luminescence in Imperfect Crystals

Georgii M. Zverev, T. N. Mikhaǐlova, Vadim A. Pashkov

Evgueni F. Martynovich, S. I. Polityko

Hermann Haken

Evgueni F. Martynovich, V. P. Dresvyanskiy, С. А. Зилов +3 more

A spatially periodic distribution of the luminescence intensity of F2 and F 3 + color centers is observed in LiF crystals with induced anisotropy. The period of spatially periodic modulation of the luminescence intensity generally coincides with the period of the change in the polarization state of excitation light. For F2 centers, the experimental axial spatially periodic dependence of the luminescence intensity is close to the calculated dependence obtained in the description of the absorption and radiative transitions in the centers by linear oscillators oriented along six C 2 axes of the cubic crystal. However, for F 3 + centers, the same experiment shows a spatially periodic distribution of luminescence intensity with a modulation period shorter by a factor of 2. It is shown that this effect of modulation frequency doubling in the spatially periodic pattern of the luminescence of color centers arises due to the nonlinear dependence of the luminescence intensity on the excitation light intensity. For F 3 + centers, upon luminescence excitation in the absorption band with λmax = 452 nm, the modulation frequency doubling is due to the saturation of the metastable triplet state of such a center.

Yanli Mao, Fei Ding, Changshun Wang +2 more

Cooperative luminescence phenomenon of Yb:YAG crystals was studied. Up-converted blue luminescence was obviously observed in Yb:YAG under excitation in the near-infrared region with a wavelength 940 nm. Experimental evidence was provided by the fact that the intensity of 498 nm luminescence shows a quadratic dependence on excitation power, and the intensity of blue luminescence increased with the increase in Yb ion concentration. It is concluded that this luminescence is due to a cooperative process resulting from a strong interaction of Yb ions. The cooperative luminescence is possiblely assigned to the strong interaction of 4f(13) electrons and neighboring Yb3+ ions in a covalent host lattice such as YAG. Theoretical cooperative luminescence spectrum was calculated.

Sergey O. Klimonsky, Alexander S. Sinitskii, Vera V. Abramova +6 more

Angular distribution of photoluminescence of trivalent rare earth ions embedded inside three-dimensional opal and inverse opal photonic crystals is experimentally shown to be strongly modulated for the emission frequencies near the first and higher photonic stop-bands. Numerical simulations of fractional density of optical states also predict highly directional emission from photonic crystals with an ideal structure. Experimental results are shown to be in a good agreement with calculated angular dependencies of luminescence. However, better agreement between experimental and theoretical data requires smoothing of calculated dependencies, which can be attributed to the presence of structural imperfections in real photonic crystal samples.