  Lead halide perovskites (MAPbX3) have emerged as promising materials for
photovoltaic and optoelectronic devices. However, their exceptional nonlinear
properties have not been fully exploited in nanophotonics yet. Herein we
fabricate MAPbX3 perovskite metasurfaces and explore their internal nonlinear
processes. While both of third-order harmonic generation (THG) and three-photon
luminescence are generated, the latter one is less affected by the material
loss and has been significantly enhanced by a factor of 60. The corresponding
simulation reveals that the improvement is caused by the resonant enhancement
of incident laser in perovskite metasurface. Interestingly, such kind of
resonance-enhanced three-photon luminescence holds true for metasurfaces with a
small period number of 4, enabling new applications of perovskite metasurface
in high-resolution nonlinear color nanoprinting and optical encoding. The
encoded information "NANO" is visible only when the incident laser is
on-resonance. The off-resonance pumping and the single-photon excitation just
produce a uniform dark or photoluminescence background.
