Highly Yb-doped oxides for thin-disc lasers

Wavelength-dependent optical gain in a KGd<inf>x</inf>Lu<inf>1&#x2013;x</inf>(WO<inf>4</inf>)<inf>2</inf>:Yb³⁺ waveguide amplifier

“…In the model, a value for the emission and absorption cross-sections was utilized that employed the values reported in the literature for KGd(WO 4 at other pump powers were investigated. A fraction of incident signal light remains uncoupled during the measurements, being neither amplified nor attenuated.…”

“…The long excited-state lifetime of RE ions, typically in the millisecond range, permits amplification without distortion of high-rate signals. The large inter-atomic distance of ~0.5 nm permits high RE dopant concentration without significant lifetime quenching [4]. Finally, these host materials provide very high absorption and emission cross-sections to the RE ions doped into them [5].…”

Potassium double tungstate waveguides with high ytterbium concentration for optical amplification

“…The radiation trapping effect, which is also known as reabsorption effect, is illustrated in Figure 4 In the absence of strong lifetime quenching effect, as in the case of KRE(WO4)2:Yb 3+ [83], a higher concentration of active ions in the material increases the occurrence of the reabsorption process and leads to the observation of longer measured lifetimes [92]. Contrarily, with the presence of strong quenching, the lifetime initially increases with the increasing active ions concentration, after which it sharply decreases with the further increase of active ion concentration [27,83] [126]. This approach requires extensive sample preparation which is destructive in nature.…”

“…Besides, the total population within each manifold will be distributed among the Stark levels. Assuming that rapid thermalisation takes place within the manifold, the fractional population at the i-th Stark level within the lower state can be deduced with the Boltzmann distribution 0 0 0 0 Similarly, the fractional population at the j-th Stark level within the upper state can be calculated using Therefore, it is often assumed that the measured luminescent lifetime represents the radiative lifetime τrad [82,83]. There are, however, a number of experimental results [77] indicating that small amount of non-radiative relaxation may occur in Yb 3+ -doped media.…”

“…The heat conduction in KRE(WO4)2 is about three times better than in silica fiber. However, it is inferior to those of the other popular laser crystals such as YAG and lutetium sesquioxide (LuO2) [83]. Hence, KRE(WO4)2 is less suitable for high-average power systems [108].…”