Gain/loss spectra in ytterbium-erbium doped bulk glass samples have been investigated within spectral range of 1.5 μm. Experimental methods for determination of the population of excited metastable level, gain/loss spectra, and their variations versus pump power have been developed. A comparison of the experimental and calculated gain/loss spectra has been done.
The partial polarization of luminescence in phosphate and silicate erbium glasses in the range of 1.5 μm under the stimulation by the linearly polarized laser light (532 nm, 790-990 nm) has been detected. The degree of polarization depends both on a spectral range of excitation and on a spectral range of registration, reaching maximum value ~1%. The concentration of depolarization has been studied.
Nonlinear upconversion quenching in high Er-doped glasses has been studied with use of Monte Carlo modeling and a new experimental steady-state technique. The experimental and simulated results exhibit that the upconversion coefficient depends on the following factors: (a) erbium content, (b) migration of excitation, (c) pump power, and (d) duration of pulse pumping.
The fluorescence and absorption variation of spectra of Er- and Yb/Er-doped phosphate and silicate glasses under CW Ti- sapphire laser were investigated. On pumping, the differential spectra demonstrated variations of spectral profiles. The reason of these variations is heating effect under high pump power. These variations were explained by a redistribution of the populations of the Stark sublevels of the 4I15/2 ground and the 4I13/2 excited manifolds. The heating effect under pumping was taken into account for measurement of quantum yield and determination of absolute values of up-conversion coefficients. Several techniques that reduce the heating effect on fluorescence, excited state absorption, and ground state absorption spectra due to pumping were proposed.
A steady-state method was used for characterization of up- conversion quenching in Er-doped glasses. This method is based on measurement of pumping dependencies of quantum yield and the population of the 4I13/2 metastable manifold. The population was determined from absorption spectra variation under the pump of semiconductor laser. The feature of the method consists in measurement of absorption spectra variation in short-wave spectral range of 300 - 520 nm. In this spectral region, a hypersensitive excited state absorption (ESA) band ((lambda) equals 478 nm) for 4I13/2 yields 4G9/2 transition was detected. The following parameters characterizing absolute intensity of ESA band were determined: line strength, integral cross- section, cross-section in maximum, and oscillator strength. This band was used for evaluation of the population of the 4I13/2 metastable manifold and up-conversion coefficients. The up-conversion coefficient, Cup equals 1.7 X 10-17 cm3s-1, was obtained for an Er3+ concentration of 6.8 X 1020 cm-3.
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