Versatile Optical Spatial Filtering Based on Multilayer Film Flat Optics

Abstract Filtering constitutes a fundamental mathematical operation that selectively transmits, modifies, or suppresses specified components of an input signal, important in electronic telecommunications, image processing, computational science, structural dynamics, and others. Optical spatial filtering, leveraging its inherent parallel capabilities and light‐speed computational efficiency, offers significant advantages in enhancing processing speed while concurrently reducing energy consumption. However, conventional optical spatial filtering systems typically necessitate auxiliary optical components and exhibit a large volume, posing the challenge of miniaturization and integration toward compact systems. Herein, the design of high‐pass, low‐pass, band‐pass, and band‐reject optical spatial filters with multilayer film flat optics is validated, offering versatile angle‐tailored filtering functionality. As a proof of concept, the high‐pass filter is employed to illustrate its pronounced edge‐enhancement capabilities for both amplitude‐ and phase‐type samples experimentally. The proposed multilayer film flat optics with geometrically simplified configurations benefit from a well‐established fabrication that is fast, low‐cost, and suitable for large‐area mass production, in stark contrast to conventional metasurfaces requiring complex unit‐cell designs, and facilitates direct integration into existing imaging systems, which holds considerable potential for enabling novel applications in optical computation, optical microscopy, and machine vision.