Up-conversion excitation of sharp Cr3+2E emission in YGG and YAG codoped with Cr3+ and Yb3+

Abstract The 2 E→ 4 A 2 emission of Cr 3+ in crystals and glasses is of great importance in science and technology. We found a new excitation mode for this emission in the garnets YGG and YAG codoped with Cr 3+ and Yb 3+ . It is based on an up-conversion mechanism using 2 F 5/2 of Yb 3+ as an intermediate state. Excitation of the Yb 3+ in the near infrared around 1000 nm leads to visible Cr 3+ 2 E→ 4 A 2 emission around 700 nm at low temperatures. The up-conversion luminescence intensity shows a strong temperature dependence due to an intrinsic loss mechanism. The up-conversion excitation spectra follow the Yb 3+ 2 F 7/2 → 2 F 5/2 absorptions. From its time dependence the up-conversion mechanism is found to be dominated by an energy transfer step: Two excited Yb 3+ ions simultaneously transfer their 2 F 5/2 excitation to Cr 3+ .