Articolele autorului Octavian Toma
Link la profilul stiintific al lui Octavian Toma

Optical and Mossbauer studies on YAG:Eu nanocrystals synthesized by a sol-gel method
Optical studies of the partially disordered crystals langasite (La3Ga5SiO14) and langatate (La3Ga5.5Ta0.5O14) doped with Eu3+
Pump wavelengths for an Er:YAG green-emitting laser
Energy transfer processes in Er-doped crystals
Dynamics of an upconversion-pumped Er:YAG laser exhibiting reabsorption losses
Modeling of a green upconversion pumped Er: YAG laser
Intrinsic limits of the efficiency of 3-µm Er:YAG laser
Structural and spectroscopical characterization of RE3+ (RE = Er, Eu, Tb) doped nanocrystalline YAG produced by a sol-gel method

Nanocrystalline YAG powders doped with Er3+, Eu3+ or Tb3+ were synthesized through a citrate-nitrate sol-gel process. Thermal treatments were applied at successively increasing temperatures in the interval 600-1400°C. The structural transformations were monitored by XRD, FT-IR and optical spectroscopy. A pure garnet phase was observed for annealing temperatures higher than 930°C.

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Effects of thermal treatment on the luminescence of YAG:Eu nanocrystals synthesized by a nitrate-citrate sol-gel method

YAG:Eu nanopowders were synthesized by the nitrate-citrate sol-gel method. The morphologic modifications of the nanocrystallites produced by the thermal treatments at various temperatures are monitored by two parameters obtained from optical fluorescence spectroscopy: intensity ratio of the transition 5D0-7F2 and 5D0-7F1 and the maximum splitting of the 7F1 level. An abrupt change of both parameters is observed at the amorphous-crystalline phase

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Emission regimes of a green Er:YLiF4 laser

We present an analysis of the emission regimes of an Er:YLiF4 laser on the transition 4S3/2 - 4I15/2, under direct pumping and various upconversion pumping mechanisms. The analysis is based on the study of the steady-state solutions of a rate equation system. The thresholds of the various emission regimes are calculated. The influence of the pump mechanism and the excited-state absorption losses on the emission regime is discussed.

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