Correction to: Nature Photonics, published online 20 May 2019.

In the version of this Letter originally published, there were some mistakes in the Supplementary Information file. In Supplementary Fig. 11, the labels of the brown and green lines incorrectly read ‘β-NaYbF4,Tm@CaF2’ and ‘β-NaYbF4,Er@CaF2’, respectively; they should have read ‘β-NaYbF4,Tm@NaYF4’ and ‘β-NaYbF4,Er@NaYF4’. In Supplementary Fig. 13, the day 7 images were duplicates of the day 0 images; the correct images have now been inserted. In Supplementary Fig. 14, the panel labels a and b were missing; they have now been added. In Supplementary Table 3, in the ‘Radiative Lifetime (ms)’ column, the average value was incorrectly given as 2.42 ms; it should have been 2.43 ms. The Supplementary Information file has now been replaced with the updated version.