# Silicon metasurfaces for third harmonic geometric phase manipulation and multiplexed holography

## TL;DR

This paper demonstrates polarization-dependent wavefront control and holography at the third-harmonic wavelength using silicon metasurfaces, enabling advanced nonlinear optical applications with high fidelity and multiplexing capabilities.

## Contribution

It introduces a novel method for nonlinear wavefront control and holography at the third harmonic using all-dielectric silicon metasurfaces with Pancharatnam-Berry phase encoding.

## Key findings

- Successful third-harmonic holography with high fidelity
- Polarization-dependent wavefront manipulation demonstrated
- Holographic multiplexing enabled via polarization states

## Abstract

Nonlinear wavefront control is a crucial requirement in realizing nonlinear optical applications with metasurfaces. Numerous aspects of nonlinear frequency conversion and wavefront control have been demonstrated for plasmonic metasurfaces. However, several disadvantages limit their applicability in nonlinear nanophotonics, including high dissipative loss and low optical damage threshold. In contrast, it has been shown that metasurfaces made of high-index dielectrics can provide strong nonlinear responses. Regardless of the recent progress in nonlinear optical processes using all-dielectric nanostructures and metasurfaces, much less advancement has been made in realizing a full wavefront control directly with the generation process. Here, we demonstrate the nonlinear wavefront control for the third-harmonic generation with a silicon metasurface. We use a Pancharatnam-Berry phase approach to encode phase gradients and holographic images on nanostructured silicon metasurfaces. We experimentally demonstrate the polarization-dependent wavefront control and the reconstruction of an encoded hologram at the third-harmonic wavelength with high fidelity. Further, we show that holographic multiplexing is possible by utilizing the polarization states of the third harmonic generation. Our approach eases design and fabrication processes and paves the way to an easy to use toolbox for nonlinear optical wavefront control with all-dielectric metasurfaces.

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Source: https://tomesphere.com/paper/1908.04999