Abstract
Abstract As an inherent characteristic of light, polarization plays important roles in information storage, display and even encryption. Metasurfaces, composed of specifically designed subwavelength units in a two-dimensional plane, offer a great convenience for polarization manipulation, yet improving their integrability and broadband fidelity remain significant challenges. Here, based on the combination of various subwavelength cross-nanofins (CNs), a new type of metasurface for multichannel hybrid polarization distribution in near-field is proposed. Sub-wavelength CN units with various waveplate (WP) functionalities, such as frequency-division multiplexing WP, half-WP and quarter-WP are implemented with high efficiency in broadband. High-resolution grayscale image encryption, multi-image storage and rapid polarization detection are demonstrated by encoding the WP pixels into single, double and four channels, respectively. All these applications possess good fidelity in an ultrabroad wavelength band from 1.2 to 1.9 µm, and the high degree of integrability, easy fabrication and multifunction make the CN-shaped WP pixels a promising candidate in optical device miniaturization, quantum applications and imaging technologies.
Highlights
In the last decade, metasurfaces are of great interest in optical researches [1, 2]
By the superposition of two circularly polarized light beams with opposite handedness based on a single metallic metasurface, the high-resolution grayscale images carried by space-variant linear polarization (LP) profile can be stored in a laser beam [11,12,13], which has fascinating applications in areas such as anticounterfeiting and information
We propose a series of cross-nanofin (CN)-shaped subwavelength WPs, which can serve as coding pixels to constitute an all-silicon metasurface with multiple hybrid polarization distributions in near-field
Summary
Metasurfaces are of great interest in optical researches [1, 2]. It offers abundant possibilities to store, hide or encrypt information because of its powerful capability for light manipulation. These characteristics enable our metasurface with the ability to manipulate information: a high-resolution grayscale image with pixels per inch (ppi) reaching 35,219, is stored and encrypted in a complex near-field hybrid polarization profile generated by a combination of different types of CN units; multiple images of alphabets or QR-codes can be encoded in different output near-field polarization profiles on a single metasurface by polarization multiplexing.
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