Super-quadratic upconversion luminescence among lanthanide ions

Area of Science:

• Materials Science
• Luminescence
• Quantum Optics

Background:

• Energy-transfer upconversion (ETU) is crucial for applications like lighting and solar energy.
• Understanding the fundamental kinetics of ETU is essential for optimizing material performance.
• Current models often simplify ETU processes, potentially limiting predictive accuracy.

Purpose of the Study:

• To investigate the relationship between direct luminescence and upconversion luminescence in Nd3+ doped crystals.
• To evaluate the validity of the commonly assumed quadratic law for ETU.
• To compare the effectiveness of existing theoretical models in describing experimental ETU decay curves.

Main Methods:

• Utilized short-pulse laser excitation on Nd3+ ions in GdVO4 and LaSc3(BO3)4 crystals.
• Measured infrared luminescence decay from the metastable 4F3/2 level.
• Measured yellow upconversion luminescence decay from the 4G7/2 level at varying doping concentrations.

Main Results:

• Observed a highly super-quadratic dependence of upconversion luminescence on direct luminescence intensity.
• Demonstrated that the standard quadratic law of ETU is insufficient.
• Found that Zubenko's model offers better fits but still fails to accurately reproduce decay curves.

Conclusions:

• The commonly assumed quadratic law for ETU is inadequate for describing observed phenomena.
• Existing models, including Zubenko's, do not fully capture the complexity of ETU, especially concerning ion distribution.
• Further refinement of theoretical models is needed to accurately predict ETU behavior in real materials.