Calcium-zinc phosphate glasses activated with Tb3+/Eu3+ for laser and white LED applications

Abstract

A spectroscopic analysis of Tb3+, Eu3+ and Tb3+/Eu3+ doped calcium-zinc phosphate glasses is carried out through their absorbance and photoluminescence spectra, and decay time profiles. Laser parameter values (stimulated emission cross section, effective bandwidth, gain bandwidth and optical gain) were obtained for the europium 5D0 → 7F2 red and terbium 5D4 → 7F5 green emissions upon 392 and 350 nm excitations, respectively, to judge the suitability of the glass phosphor for fiber lasers. The Tb3+/Eu3+ activated phosphor tonality can be shifted from reddish-orange of 1744 K upon 376 nm excitation to warm white of 3560 K and neutral white of 4414 K upon 370 and 368 nm excitations, respectively. From decay time profiles of the terbium 5D4 and 5D3 levels in the co-doped glass is inferred that Eu3+ can be sensitized by Tb3+ through a non-radiative energy transfer. An electric dipole-dipole or quadrupole-dipole interaction into Tb3+ - Eu3+ clusters could be the dominant mechanism in the Tb3+ to Eu3+ energy transfer. Tb3+ and/or Eu3+ activated calcium-zinc phosphate glasses, pumped by UV LED chips, could be appropriate phosphors for the development of materials emitting neutral/warm white light, reddish-orange light or green/red laser light.