  All-inorganic CsPbBr3 perovskite colloidal quantum dots have recently emerged
as promising material for a variety of optoelectronic applications, among
others for multi-photon-pumped lasing. Nevertheless, high irradiance levels are
generally required for such multi-photon processes. One strategy to enhance the
multi-photon absorption is taking advantage of high local light intensities
using photonic nanostructures. Here, we investigate two-photon-excited
photoluminescence of CsPbBr3 perovskite quantum dots on a silicon photonic
crystal slab. By systematic excitation of optical resonances using a pulsed
near-infrared laser beam, we observe an enhancement of two-photon-pumped
photoluminescence by more than one order of magnitude when comparing to using a
bulk silicon film. Experimental and numerical analyses allow relating these
findings to near-field enhancement effects on the nanostructured silicon
surface. The results reveal a promising approach for significant decreasing the
required irradiance levels for multi-photon processes being of advantage in
applications like low-threshold lasing, biomedical imaging, lighting and solar
energy.
