Ca1−XYbXF2+X
crystals were grown by two different methods: simple melting under
CF4
atmosphere and the laser heated pedestal growth (LHPG) method under
Ar atmosphere. Spectroscopic characterization (absorption, emission, Raman
spectroscopy and decay curves) was carried out to identify Stark levels of
Yb3+
transitions in the different crystallographic sites of the cubic structure in
Ca1−XYbXF2+X crystals.
The Yb3+
concentration dependence of the experimental decay time was analysed by using concentration
gradient fibre in order to understand involved concentration quenching mechanisms. Under
Yb3+ ion
infrared pumping, self-trapping and up-conversion non-radiative energy transfer to unexpected rare earth
impurities (Er3+, Tm3+) has been observed in the visible region and interpreted by a limited diffusion process within the
Yb3+
doping ion subsystem towards impurities. The main parameters useful
for a theoretical approach of laser potentiality have been given as
τrad = 2.05 ms,
N0 = 7.47 × 1021 cm−3 (32 mol%)
and Nm = 6.39 × 1021 cm−3
(26.5 mol%).
Two major fiber crystal growth methods have been applied for the synthesis and spectroscopic characterizations of Yb3+-doped Y3Al5O12 (Yb:YAG) to show the feasibility of a flexible single crystal fiber laser. One is the micropulling-down (μ-PD) method and the other is the laser heated pedestal growth (LHPG) method. 500 mm length fiber with no Yb segregation has been grown by the μ-PD method. A detailed analysis of Yb:YAG spectroscopy is made to contribute to the discussion on the determination of energy levels. On the other hand, a combinatorial chemistry approach has been applied on concentration gradient crystal fibers grown by the LHPG method allowing the measurement of the intrinsic radiative lifetime and the analysis of concentration quenching processes of Yb3+ ions in YAG.
Full concentration range of Lu 2x Gd 2-2x SiO 5 (LGSO:Ce) crystals was grown by the Czochralski method. Dependence of scintillation properties on composition (х) in the range of solid solutions is established. It was determined that LGSO:Ce scintillation yield increases in the range 0.3<х< 0.8 and reaches 29000 phot/MeV at 60% of Lu in the host (x=0.6), and energy resolution improves up to 6.7 % at 662 KeV. The observed light yield increase, surprisingly high Ce
For the next generation of calorimeters, designed to improve the energy resolution of hadrons and jets measurements, there is a need for highly granular detectors requiring peculiar geometries. Heavy inorganic scintillators allow compact homogeneous calorimeter designs with excellent energy resolution and dual-readout abilities. These scintillators are however not usually suited for geometries with a high aspect ratio because of the important losses observed during the light propagation. Elongated single crystals (fibers) of Lutetium Aluminium garnet (LuAG, Lu 3 Al 5 O 12 ) were successfully grown with the micropulling-down technique. We present here the results obtained with the recent fiber production and we discuss how the light propagation could be enhanced to reach attenuation lengths in the fibers better than 0.5 m.
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