Doubly resonant nonlinear metasurfaces enabling NIR-to-UV upconversion for reconfigurable Fourier optical processing

TL;DR

This paper introduces a reconfigurable nonlinear metasurface that enables efficient near-infrared to ultraviolet upconversion for Fourier optical processing, allowing tunable image manipulation at short wavelengths in compact platforms.

Contribution

The work demonstrates a doubly resonant nonlinear metasurface supporting specific resonances for enhanced efficiency and reconfigurable Fourier optical processing in the UV range, a novel approach in metasurface design.

Findings

Achieved UV image generation via degenerate four-wave mixing.

Demonstrated directional and tunable filtering at UV wavelengths.

Enhanced nonlinear process efficiency through tailored resonances.

Abstract

Fourier optical processing underpins optical information manipulation, yet extending such operations to short wavelengths within compact platforms remains challenging. Here, we address this challenge by embedding reconfigurable Fourier-domain processing within IR-to-UV upconversion in a doubly resonant nonlinear metasurface. When coherently illuminated at the Fourier plane with an image-bearing signal and a spatially structured pump, the metasurface generates UV images via degenerate four-wave mixing. Crucially, the spatial-frequency content of these upconverted images is selectively shaped by the tailored spectrum of the pump. To boost the efficiency of this nonlinear process, the metasurface is designed to simultaneously support a toroidal dipole bound state in the continuum and a magnetic dipole resonance, providing spectrally aligned and independently enhanced field localization for signal and pump beams, respectively. Building on this architecture, we experimentally demonstrate directional and continuously tunable filtering at the upconverted UV wavelengths. These results establish nonlinear metasurfaces as a versatile platform for Fourier optics and reconfigurable all-optical image processing.