1.5-μm infrared excitation of visible luminescent in Y1−xErxF3 and Y1−x−yErxTmyF3 via resonant-energy transfer

Abstract

Intense visible emission in the red, green, and blue has been observed from infrared to visible multiphoton Y_1−xEr_xF₃ upconversion phosphors pumped with 1.5‐μm radiation from InGaAsP‐laser sources. With 0.01<x4S_3/2 level of Er³⁺. The addition of Tm³⁺ in the 0.001–0.02 range preferentially quenches the emission from the higher‐energy Er³⁺ levels resulting in a red visible emission originating on the Er^{3+ 4}F_9/2 level. The phosphors are useful visible monitors of focused 1.5‐μm semiconductor laser and unfocused F‐center laser radiation. The unexpectedly high brightness in the visible may be attributed to thermal equilibration, where the excitation is trapped in the higher lying states after each upconversion step.