Ultralarge anti-Stokes lasing through tandem upconversion.

Coherent ultraviolet light is important for applications in environmental and life sciences. However, direct ultraviolet lasing is constrained by the fabrication challenge and operation cost. Herein, we present a strategy for the indirect generation of deep-ultraviolet lasing through a tandem upconversion process. A core-shell-shell nanoparticle is developed to achieve deep-ultraviolet emission at 290 nm by excitation in the telecommunication wavelength range at 1550 nm. The ultralarge anti-Stokes shift of 1260 nm (~3.5 eV) stems from a tandem combination of distinct upconversion processes that are integrated into separate layers of the core-shell-shell structure. By incorporating the core-shell-shell nanoparticles as gain media into a toroid microcavity, single-mode lasing at 289.2 nm is realized by pumping at 1550 nm. As various optical components are readily available in the mature telecommunication industry, our findings provide a viable solution for constructing miniaturized short-wavelength lasers that are suitable for device applications.