Luminescence and decay behaviour of Tb3+:ZrF4-BaF2-LaF3-YF3-AlF3-NaF optical glasses

The present investigation aims at elucidating the photoluminescence behaviour of Tb3+ doped 53ZrF4-20BaF2-2LaF3-2YF3-3AlF3-(20-x)-NaF-xTbF3 (where x=0.2,0.4,0.6,0.8,1.0,1.5 and 2.0 mol%) optical glasses. We have measured two prominently intense emission blue group bands (5D3→7Fj=6,5,4,3 at 382, 415, 436 and 461 nm) and green group bands (5D4→7Fj=6,5,4,3 at 488, 544, 584 and 623 nm) with an excitation at λexc=229 nm (4f8→4f75d1) from these ZBLYAN glasses. Under a UV source (15 W), more prominent and rich green luminescent colour (544 nm) has been noticed from these terbium glasses. In particular, glass with low Tb3+ (0.2 mol%) content has displayed the emission transitions of 5D3→7Fj=6,5,4,3 and at still higher concentrations these emission bands have disappeared completely because of resonant energy transfer phenomenon or cross-relaxation process. The mechanism behind such a process has been explained in terms of an energy level diagram. Among the seven-terbium glasses, one glass with 1.0 mol% of Tb3+ (as the optimum content) has revealed an intense green emission