Lasing in spherically shaped Y$_2$O$_3$–ZnO nanocomposites

The luminescence properties of spherically shaped Y$_2$O$_3$–ZnO nanocomposites with average diameters of 132 and 179 nm are studied. The nanocomposites are produced by synthesis from a solution, and their size dispersion is about 15%. Narrow peaks of lasing upon exciton radiative recombination in zinc oxide are observed in the ultraviolet spectral region. It is shown that, for small cavities (100–200 nm in diameter), individual nanospheres of the composite exhibit only one laser mode. The initiation of stimulated luminescence with a peak at 376 nm corresponding to the bound photon mode of nanocavities 179 nm in diameter is observed as the optical pumping power is increased to $>$ 130 kW cm$^{-2}$.