Deep UV random lasing from NaGdF4:Yb3+,Tm3+ upconversion nanocrystals in amorphous borosilicate glass

The realization of lanthanide-doped upconversion nanocrystals embedded in a robust and transparent solid medium is highly desired to achieve deep UV ( < 300 n m ) lasing. Here, we fabricate N a G d F 4 : Y b 3 + , T m 3 + upconversion nanocrystals inside amorphous borosilicate glass to support ∼ 290 n m random lasing emission under 980 nm excitation. We found that with careful control of the growth process, which is the key to achieve high-crystallinity nanocrystals, the nanocrystals can suppress defect-related quenching and enhance 1 I 6 → 3 H 6 ( 6 I J → 8 S 7 / 2 ) transition of T m 3 + ( G d 3 + ) ions under five-photon absorption excitation so that high optical gain ( > 45 c m − 1 ) at ∼ 290 n m can be obtained.