Polarization Imaging and Edge Detection with Image-Processing Metasurfaces

TL;DR

This paper demonstrates the design of polarization-sensitive and polarization-independent optical metasurfaces capable of performing edge detection and Laplacian operations on images, enabling efficient, tunable, and isotropic analog image processing.

Contribution

It introduces novel single-layer silicon metasurfaces with tailored polarization responses for advanced, on-the-fly image processing functionalities, including dynamic direction-dependent edge detection.

Findings

Metasurfaces achieve efficient Laplacian edge detection with large numerical apertures.

Asymmetric polarization responses enable tunable, direction-dependent image processing.

Dual-polarized metasurfaces operate effectively on unpolarized or arbitrarily polarized images.

Abstract

Optical metasurfaces have been recently explored as ultrathin analog image differentiators. By tailoring the momentum transfer function, they can perform efficient Fourier-filtering - and thus potentially any linear mathematical operation - on an input image, replacing bulky 4f systems. While this approach has been investigated in different platforms, and several techniques have been explored to achieve the required angular response, little effort has been devoted so far to tailor and control also the polarization response of an image-processing metasurface. Here, we show that edge-detection metasurfaces can be designed with tailored polarization responses while simultaneously preserving an isotropic response. In particular, we demonstrate single-layer silicon metasurfaces yielding efficient Laplacian operation on a 2D image with either large polarization asymmetry, or nearly polarization-independent response. In the former case, we show that a strongly asymmetric polarization response can be used to unlock more sophisticated on-the-fly image processing functionalities, such as dynamically tunable direction-dependent edge detection. In parallel, metasurfaces with dual-polarized response are shown to enable efficient operation for unpolarized or arbitrarily polarized images, ensuring high efficiency. For both devices, we demonstrate edge detection within relatively large numerical apertures, with excellent isotropy and intensity throughput. Our study paves the way for the broad use of optical metasurfaces for sophisticated, massively parallel analog image processing with zero energy requirements.