Quantum cutting mechanism in NaYF_4:Tb^3+, Yb^3+

A quantum cutting mechanism for the sublinear near-IR power dependence property in Tb3+-Yb3+ codoped NaYF4 powders were investigated both experimentally and theoretically. The slopes of Yb3+ luminescence intensity versus excitation power were fitted to be between 0.5 and 1. We have developed a quantum cutting rate equation model to explain the anomalous sublinear phenomenon and an assessment factor was introduced to help understand the physical mechanism. Experimental results showed that the linear downconversion process combined with second-order nonlinear process induced the sublinear power dependence property with the latter to be the dominant process.