No abstract

No abstract

When pumped by radiation from a Si–GaAs diode, the luminous efficiency of Y3OCl7:Yb3+, Er3+ is comparable to that of visible emitting GaP diodes. By varying the Yb3+ concentration, phosphors have been made which produce a red or yellow visual response.

No abstract

Intense visible emission in the red, green, and blue has been observed from infrared to visible multiphoton Y1−xErxF3 upconversion phosphors pumped with 1.5-μm radiation from InGaAsP-laser sources. With 0.01<x<0.2, the dominant emission is in the green corresponding to transitions from the 4S3/2 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 Er3+ 4F9/2 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.