Wavefront shaping of infrared light through a subwavelength hole

TLDR

Light transmission through subwavelength holes in metal films, enhanced by plasmonic effects, can be engineered to shape the emerging beam, enabling complex patterns and broad applications in holography and imaging. We design a silver thin‑film hole surrounded by groove patterns via surface‑wave holography, and through simulations and experiments demonstrate that the infrared wavefront can be shaped into prescribed patterns such as letters “L” or “O” at a specific location. The experiments confirm that groove‑patterned holes can produce arbitrary infrared wavefronts, deepening understanding of subwavelength transmission and opening avenues for wave manipulation and sensing.

Abstract

Light passing through a subwavelength hole in an opaque plate is a fundamental concern in both optical science and applications. Using both simulations and experiments, we show that, when a subwavelength hole in a silver thin film is surrounded by well-designed patterns of grooves, the wavefront of the infrared light through it can be shaped into a preset complicated pattern such as a Latin letter 'L' or 'O' at a given position instead of being diffracted in all directions. The design is created via the surface-wave-holography method, which allows direct determination of the surface plasmonic structure for a given wavefront-engineering functionality without the need to solve complex inverse problems. The results will deepen current understanding of this enduring issue and will find applications in many fields such as wave manipulation and sensing. Researchers have shown how passing a light beam through a tiny hole in a thin metallic film can be used to modify the beam's shape. Modifying light as it passes through a material is a key functionality for many optical devices. Holes in metal films are known to enhance light transmission through plasmonic effects—collective motions of electrons on the metal surface. Zhi-Yuan Li and colleagues at the Institute of Physics, Chinese Academy of Sciences, China, showed that patterning the surface of the metal film with grooves allows the light emerging on the other side to take almost any shape. Such functionality could find a wide range of applications in holography or optical imaging.