Lithium yttrium ytterbium fluoride nanocrystals for laser cooling applications

This paper reports on successful synthesis and comprehensive characterization of lithium yttrium ytterbium fluoride nanocrystals. The Yb content was varied between 1% and 10%. The nanocrystals emit in near-infrared, with the emission spectrum extending from 960 nm to 1060 nm when excited with the 900-nm light. Strong anti-Stokes photoluminescence was observed when using excitation wavelengths ranging from 1000 nm to 1020 nm. The temperature dependence of the Stokes and anti-Stokes photoluminescence was measured over the range from 10 °C till 70 °C. These nanocrystals have a high potential to be used in optical cooling applications.