Intense and broadband mid-infrared emission by nano-crystallization of rare‐earth doped oxyfluoride glass-ceramic

Transparent oxyfluoride glass ceramics (GCs) comprised of a uniform oxide glass phase and a well-distributed fluoride crystal phase are regarded as suitable optical gain materials because of the combination of facile fabricability of glass and low phonon energy of nanocrystals. Here, oxyfluoride GCs containing NaYF4: Er3+/Ho3+/Dy3+ nanocrystals were controllably prepared. Due to the preferential incorporation of rare-earth ions into NaYF4 nanocrystals with low phonon energy and the efficient energy transfer between active ions, enhanced and broadband mid-infrared (MIR) emission at 2.5–3.3 µm was obtained from the GCs, which was nearly unobserved in precursor glass (PG) because of the high phonon energy of glass matrix. Compared with Er3+ singly-doped sample, the full width at half maximum (FWHM) is more than 3 times broader in Er3+/Ho3+/Dy3+ triply-doped sample. Furthermore, by the match of the refractive index of glass with NaYF4 nanocrystal, transparent GCs with average crystal size of 80 nm and high transmittance over 80% were achieved simultaneously. The desirable optical properties endow the GCs with potential applications in MIR broadband tunable lasers.