Plasmonic Metalens for Narrowband Dual‐Focus Imaging

• Published in: Advanced optical materials Vol. 5; no. 24
• Main Authors: Williams, Calum, Montelongo, Yunuen, Wilkinson, Timothy D.
• Format: Journal Article
• Language: English
• Published: 15.12.2017
• Subjects: diffractive lenses; holographic optical elements; metasurfaces; plasmonics; polarization‐selective devices; subwavelength structures
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.201700811

A new type of metalens with the capability to selectively focus narrowband light is reported at different focal planes depending on polarization. Two zone planes with two different focal lengths are spatially multiplexed and encoded in the subwavelength regime with arrays of orthogonal silver nanostructures, which are designed to exhibit strong wavelength‐ and polarization‐dependent scattering profiles. Using this principle, imaging under white‐light illumination with independent focal planes is experimentally demonstrated for each polarization at the narrowband resonant wavelength. Furthermore, each focal plane can be dynamically controlled with an output polarizer. In contrast to conventional refractive and diffractive optical elements, functional metalenses allow additional control over wavelength and polarization properties of light for a wide range of applications. A plasmonic metalens, which selectively focuses narrowband light at different focal planes depending on polarization is demonstrated. Arrays of orthogonal anisotropic silver nanostructures exhibiting strong wavelength‐ and polarization‐dependent scattering profiles are used to encode two different focal length zone plates. The metalens is used to image under white‐light illumination and two independent focal planes, for each polarization, at the narrowband resonant wavelength are achieved.