Spectroscopic and generation characteristics of $\mathrm{NaLaGd}$ double tungstates and molibdates doped with $\mathrm{Nd}^{3+}$ and $\mathrm{Tm}^{3+}$ ions

In this paper, we report the results of the study of the spectroscopic properties of $\mathrm{NaLa_{1/2}Gd_{1/2}(WO_4)_2:Nd}$ crystals and $\mathrm{Tm}^{3+}$-doped mixed $\mathrm{NaLaGd}$ double tungstates (molybdates) with scheelite structure. We analyzed the low-temperature absorption spectra of $\mathrm{NaLa_{1/2}Gd_{1/2}(WO_4)_2:Nd}$ crystals and compared the oscillator strengths of the hypersensitive transition $\mathrm{^4I_{9/2}\to{}^4G_{5/2}+{}^2G_{7/2}}$ of $\mathrm{Nd}^{3+}$ ions in $\mathrm{NaLa_{1/2}Gd_{1/2}(WO_4)_2:Nd}$ crystals and the oscillator strengths of the hypersensitive transitions $\mathrm{^3H_6\to{}^3H_4}$, $\mathrm{^3H_6\to{}^3F_4}$ of $\mathrm{Tm}^{3+}$ ions in the crystals of mixed NaLaGd double tungstates (molybdates) having scheelite structure with the analogous values in other oxide crystals with the corresponding activators. We made a conclusion about the reduction of the point symmetry of rare-earth ions in these crystals. We also present the results of the experiment on laser generation in the crystals of $\mathrm{Tm}^{3+}$-doped mixed NaLaGd double tungstates (molybdates) with scheelite structure.