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Title: From the up-converting multimodal luminescent thermometer to ratiometric visual power density meter based on Er3+ ,Yb3+ emission

Authors: A. Javaid, M. Szymczak, L. Marciniak

Journal: Materials Horizons

DOI: 10.1039/D5MH01369K   

Recent studies conducted by Marciniak’s group on Na₃Sc₂(PO₄)₃:Er³⁺,Yb³⁺ have shown that under 980 nm excitation, in addition to the characteristic for Er³⁺,Yb³⁺ co-doped systems emission bands (arising from the electronic transitions ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2), additional emission band related to the ²H_9/2 → ⁴I_13/2 transition was also observed. Temperature-dependent spectroscopic measurements of these systems revealed a series of changes in the relative intensities of the emission bands, enabling the use of this material in luminescence thermometry.

Most importantly, due to the different population mechanisms of the ⁴S_3/2 and ⁴F_9/2 levels, a pronounced and monotonic influence of temperature on the green-to-red luminescence intensity ratio was observed. This effect, combined with optical heating induced by the excitation beam, whose efficiency increases with the concentration of sensitizer ions, allowed for the development of a visual optical power density sensor.

The application of Na₃Sc₂(PO₄)₃:Er³⁺,Yb³⁺ for this purpose enabled not only local readout of the power density values using luminescence intensity ratio (LIR) analysis and CIE1931 chromaticity coordinates, but, more importantly, also facilitated two-dimensional imaging of the optical power density distribution through analysis of the signals recorded in the red and green channels of a digital camera.

To the best of our knowledge, this represents the first reported visual luminescence-based optical power density sensor and the first demonstration of its use for two-dimensional imaging of optical power density. 

This work was funded by the NCN Opus project UMO- 2022/45/B/ST5/01629.