Yttrium Oxide Upconverting Phosphors. Part 4: Upconversion Luminescent Emission from Thulium-Doped Yttrium Oxide under 632.8-nm Light Excitation

Strong blue upconversion emission has been observed from Y 2 O 3:Tm 3+ phosphors under 632.8-nm excitation, in addition to weaker green and red emissions. All of these emissions, including the red, showed a two-photon intensity dependence on the incident 632.8-nm laser power. The emissions that showed only a one-photon intensity dependence occurred in the near-IR region of the spectrum. The mechanism for the origins of these emissions was derived from temperature studies over the range of 0 to −190 °C and their dependence on the laser power at room temperature. Energy values are derived for all of the Tm 3+ levels in the cubic Y 2 O 3 lattice between the 3 H 6 ground state and the 1 D 2 excited state at ca. 27 500 cm -1 from the positions of the emission bands.