Efficiently strengthen and broaden 3 μm fluorescence in PbF2 crystal by Er3+/Ho3+ as co-luminescence centers and Pr3+ deactivation

Energy Transfer and Cross-Relaxation Induced Efficient 2.78 μm Emission in Er3+/Tm3+: PbF2 mid-Infrared Laser Crystal

“…The raw materials were weighed and thoroughly mixed. The process of crystal growth was similar to our previous work [37]. The melt was homogenized in a covered graphite crucible in a high-temperature zone at 1000 • C for 8 h, and the crystal growth process was driven by lowering the graphite crucible at a speed of 0.5 mm/h.…”

“…Figure 1 shows the XRD patterns and refined XRD patterns of the Er: PbF 2 , Tm: PbF 2 , Er/Tm: PbF 2 crystals, and the JCPDS standard card of the PbF 2 crystal (nos. 06-2051) [37]. The residuals of refinements (fit profiles shown in Figure 1) of Er: PbF 2 , Tm: PbF 2 , Er/Tm: PbF 2 crystals were 9.61%, 7.71%, 10.17%, respectively.…”

“…Figure 3 illustrates the room temperature absorption spectra of Er: PbF2, Tm: PbF2, and Er/Tm: PbF2 crystals ranging from 400 nm to 2200 nm. Clearly, the typical absorption bands centered at approximately 417, 451, 486, 521, 541, 650, 802, 975, and 1509 nm in the Er: PbF2 crystal originated from the transitions from the ground state 4 I15/2 level to upper-lying 2 H9/2, 4 F5/2,3/2, 4 F7/2, 2 H11/2, 4 S3/2, 4 F9/2, 4 I9/2, 4 I11/2 and 4 I13/2 levels of Er 3+ ion, respectively [37]. While in the Tm: PbF2 crystal mainly five absorption bands of Tm 3+ ion are labeled, the absorption peaks centered at round 464, 680, 792, 1211, and 1618 nm are in accord with the transitions from ground state 3 H6 level to upper-lying 1 G4, 3 F2,3, 3 H4, 3 H5 and 3 F4 levels, respectively.…”

“…Some fluoride crystals have low thermal conductivity, such as CaF 2 and SrF 2 . The PbF 2 crystal has high thermal conductivity (28 W/m/K) and stable mechanical and chemical properties [36,37]. Consequently, with these favorable characteristics, the PbF 2 crystal may be selected as a promising host material.…”