Excited State Absorption and Thermoluminescence in Ce and Mg Doped Yttrium Aluminum Garnet
K. Wiśniewskia, Cz. Koepkea, A.J. Wojtowicza, W. Drozdowskia, M. Grinbergb, S.M. Kaczmarekc and J. Kisielewskid
a Institute of Physics, Nicholas Copernicus University, Grudziądzka 5/7, 87-100 Toruń, Poland
b Institute of Experimental Physics, Gdańsk University, Wita Stwosza 57, 80-952 Gdańsk, Poland
c Institute of Optoelectronics, Military University of Technology, 01-489 Warsaw, Poland
d Institute of Electronic Materials Technology, 01-919 Warsaw, Poland
Received: September 16, 1998; in final form January 29, 1999
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In this paper we report preliminary results of optical studies on Y3Al5O12 (YAG) crystals codoped with Ce and Mg. By using measurements of luminescence, absorption, and luminescence excitation spectra we demonstrate that although the basic features introduced to the YAG host by the Ce-doping remain intact, the Mg-codoping imposes some significant changes on other properties of the material. These changes are potentially important for laser and/or scintillator applications of YAG:Ce and are due, most likely, to modifications of defect populations in the material. We characterize them by using the techniques of thermoluminescence and excited state absorption under excimer laser pumping. These techniques, interestingly, yield results that seem inconsistent. While the thermoluminescence signal of the Mg-doped sample is strongly reduced, suggesting that trap concentrations in the presence of Mg are suppressed, the excited state absorption signal, which we also relate to the traps, is higher. We offer a tentative explanation of this contradiction between the two experiments that involves a massive transfer of electrons from the Mg-related defects to the excited state absorption centers caused by the excimer pump itself.
DOI: 10.12693/APhysPolA.95.403
PACS numbers: 78.55.Hx, 78.55.-m, 78.60.Kn, 73.50.Gr, 29.40.Mc, 78.20.-e, 78.20.Wc, 78.40.-q,