Abstract

Due to the simple energy structure of Yb³⁺ with only two 4f manifolds, energy transfer processes such as cross-relaxation and up-conversion are not expected in Yb-doped materials. Yet, photoconductivity measurements have confirmed the creation of free charge carriers in Yb-doped single crystals when irradiated with pump light of 940nm [1,2]. These experiments focussed particularly on Yb:YAG samples of various doping concentrations and the measurements displayed a nonlinear increase of photocurrent with the excitation density. Further investigations of Yb:YAG ceramics as well as Yb:Lu₂O₃ show a similar behaviour, indicating that this phenomenon is neither limited to crystalline samples nor to the YAG host. Yet, a different behaviour is observed in Yb-doped fluorides which may be due to the host's different band structure.

© 2009 IEEE