Fig. 2: Emission spectra and decay dynamics as a function of Yb³⁺ concentration.

a Emission spectra of YBO₃ doped with 0.1% Tm³⁺ and increasing Yb³⁺ concentration as indicated in the plot, excited in the Tm^{3+ 1}G₄ level. The emission bands at 10,000 cm⁻¹ and 12,000 cm⁻¹ are due to radiative relaxation of the Yb^{3+ 2}F_5/2 and Tm^{3+ 1}G₄ levels (with overlap of ³H₄ → ³H₆ emission), respectively. b Same as in a, but for YAG. The Tm³⁺ concentration is 0.03% in these samples. c Same as in a, but for Y₂O₃. The Tm³⁺ concentration is 0.1% in these samples. d Same as in a, but for NaYF₄. The Tm³⁺ concentration is 0.3% in these samples. e–h Photoluminescence decay curves of the ¹G₄ level measured for the ¹G₄ → ³F₄ emission (~650 nm) from the same samples studied in a–d, using the same colour coding. These results show accelerated decay due to energy transfer at increasing Yb³⁺ concentration. All experiments were performed by exciting Tm³⁺ to the ¹G₄ level (~465 nm)