Laser Refrigeration of Ytterbium-Doped Sodium-Yttrium-Fluoride Nanowires

Sodium yttrium fluoride (β-NaYF₄ ) nanowires (NWs) with a hexagonal crystal structure are synthesized using a low-cost hydrothermal process and are shown to undergo laser refrigeration based on an upconversion process leading to anti-Stokes (blueshifted) photoluminescence. Single-beam laser trapping combined with forward light scattering is used to investigate cryophotonic laser refrigeration of individual NWs through analysis of their local Brownian dynamics.