Fig. 1: X-ray diffraction pattern of the Er3+,Yb3+:YAG transparent ceramics (black dots), results of Rietveld refinement analysis (red curve) and their difference (blue curve) for a) Er(0.5)Yb(<0.01), b) Er(0.5)Yb(5), c) Er(0.5)Yb(10), and d) Er(0.5)Yb(20) samples; e) the change of bond lengths (black, and red dot) and their average distance (blue dot) of dodecahedral site (Y3+, Yb3+, Er3+); f) the change of lattice parameter (black dots) and bond distortion of dodecahedral site (red dots) with the change on Yb3+ concentrations. Fig. 3: Optical absorption spectra of Er3+,Yb3+:YAG transparent ceramics. Fig. 4: Emission spectra of Er3+,Yb3+:YAG transparent ceramics (λexc = 940 nm, T – 300 K): a) Er(0.5)Yb(20) sample measured at the edge (black line) and in the middle (red line); b) normalized emission spectra of Yb3+ ions; c) anti-Stokes and d) stokes emission. Fig. 6: Normalized emission spectra of Er3+ ions measured in the range of 1400–1600 nm in Er3+,Yb3+:YAG transparent ceramics. The inset shows the emission spectrum of Er(0.5)Yb(20) sample measured in the range of 1400-1700 nm with a manually corrected background. Fig. 7: Luminescence decay curves of 1531 nm and 1028 nm emission of transparent Er3+,Yb3+:YAG ceramics at λexc = 940 nm. Fig. 8: The measured spectra of integration sphere setup under laser diode excitation (λmax = 940 nm, T – 295K) and Er3+,Yb3+:YAG transparent ceramics inside