  Nonlinear metasurface holography shows the great potential of metasurfaces to
control the phase, amplitude, and polarization of light while simultaneously
converting the frequency of the light. The possibility of tailoring the
scattering properties of a coherent beam, as well as the scattering properties
of nonlinear signals originating from the meta-atoms facilitates a huge degree
of freedom in beam shaping application. Recently, several approaches showed
that virtual objects or any kind of optical information can be generated at a
wavelength different from the laser input beam. Here, we demonstrate a
single-layer nonlinear geometric-phase metasurface made of plasmonic
nanostructures for a simultaneous second and third harmonic generation.
Different from previous works, we demonstrate a two-color hologram with
dissimilar types of nanostructures that generate the color information by
different nonlinear optical processes. The amplitude ratio of both harmonic
signals can be adapted depending on the nanostructures' resonance as well as
the power and the wavelength of the incident laser beam. The two-color
holographic image is reconstructed in the Fourier space at visible wavelengths
with equal amplitudes using a single near-infrared wavelength. Nonlinear
holography using multiple nonlinear processes simultaneously provides an
alternative path to holographic color display applications, enhanced optical
encryption schemes, and multiplexed optical data-storage.
