Numerical investigation of reverse cross-relaxation process in Tm-doped glass by fitting 3H4 fluorescence decay tail

Structural and optical properties in Tm3+/Tm3+–Yb3+ doped NaLuF4 glass‐ceramics

“…Similar spectra are obtained for the glass and glass‐ceramic samples, but the ratio of the emission intensity of the transition 3 H 4 → 3 F 4 to that of the 3 F 4 → 3 H 6 decreases with increasing Tm 3+ concentration as is shown in Figure 5. This reduction in the intensity of the 1450 nm emission with concentration has been attributed to cross‐relaxation between 3 H 4 → 3 F 4 and 3 F 4 → 3 H 6 transitions that enhance the latter 45,46 …”

“…Then, a second energy transfer process involving Yb 3+ and Tm 3+ ions can occur through the mechanism 2 F 5/2 → 2 F 7/2 (Yb 3+ ): 3 F 4 → 3 F 2,3 (Tm 3+ ) (ET2). Subsequent multiphonon relaxation from level 3 F 2,3 populates the 3 H 4 state and a third energy transfer upconversion process, 2 F 5/2 → 2 F 7/2 (Yb 3+ ): 3 H 4 → 1 G 4 (Tm 3+ ) (ET3) populates the 1 G 4 state 46 …”

“…This reduction in the intensity of the 1450 nm emission with concentration has been attributed to cross-relaxation between 3 H 4 → 3 F 4 and 3 F 4 → 3 H 6 transitions that enhance the latter. 45,46 The emission spectra of the codoped samples obtained under the same experimental conditions by exciting at 791 nm show, in addition to the Tm 3+ emissions around 1450 and 1650 nm, the Yb 3+ ( 2 F 5/2 → 2 F 7/2 ) emission around 1000 nm. The presence of the Yb 3+ emission after excitation of Tm 3+ ions confirms the energy transfer from Tm 3+ to Yb 3+ ions.…”

“…49 The UC processes involved in the population of the relevant emitting states of Tm 3+ ion are depicted in Figure 9. Firstly, the Yb 3+ ion at the ground state was excited to the 2 F 5/2 state by absorbing one 975 nm photon and then transferred the energy to Tm 3+ ions in the ground state following the mechanism 2 46 To obtain information about the processes involved in the UC emission after 975 nm excitation, the UC emission spectra have been obtained at different pump power densities. The dependence of the UC emission on the pump power density is related to the number of photons (n) involved in the process and gives information about the UC mechanisms according to the relation Figure 10 shows the logarithmic plot of the UC blue and NIR ( 3 H 4 → 3 H 6 ) emission intensities of the co-doped GC sample with 0.5TmF 3 −1YbF 3 (in mol%) as a function of the pump power laser density.…”