Ultra-high NA optical image differentiator based on dielectric metasurfaces.

Metasurface-based optical differentiators have recently attracted attention for their potential advantages in real-time and high-throughput image processing technology. However, the existing differentiators suffer from limitations in numerical aperture (NA). Here, we propose a differential metasurface based on silicon clusters covered with polydimethylsiloxane, achieving a remarkable NA of 0.7. We numerically demonstrate the proposed differentiator can perform second-order differentiation on a 1D spatial function and high NA can accurately compute smaller-scale variations. We further demonstrate its ability to achieve edge detection on 2D images. Our results advance the development of ultra-high numerical aperture optical differentiator and provide new opportunities for image processing. [ABSTRACT FROM AUTHOR]