Tunable Water‐Based Meta‐Lens

Abstract

Water, the source of life, is a more abundant, low‐cost, and environment‐friendly candidate material for tunable meta‐devices compared to conventional approaches in the microwave region. Wavefront shaping can be flexibly manipulated by adjusting the shapes and temperature of water‐based meta‐atoms, but individual control of each meta‐atom is complicated and inconvenient, especially for continuous tunability. Here, we propose a design strategy based on the phase compensation mechanism to continuously tune the properties of water‐based meta‐lenses at 5 GHz. Integrated‐resonant units (IRUs) with coupled water pillars are carefully designed to effectively tailor the balance between polarization conversion efficiency and phase compensation. By changing the filling height of water in the designed meta‐lens from 10 to 60 mm, the focal length can be tuned from 228 to 424 mm. The off‐axis focusing of the meta‐lens is also demonstrated in which the deflection angle is adjustable from around 0° to 5°. This work will pave the way for designing tunable water‐based meta‐devices and facilitating their applications in microwave imaging systems.

Independent Manipulations of Transmitting and Receiving Channels by Nonreciprocal Programmable Metasurface

“…Programmable metasurfaces have huge capability to control the spatial EM beams in real time, − since the EM features of the unit cells can be manipulated by external DC voltages in a programmable way. Generally, the programmable metasurfaces can be broadly classified into two categories: reflection type , and transmission type. − The reflection-type design is limited by the presence of blocking effects, and both types exhibit disadvantages of high profile.…”

Integrated-Resonant Units for Phase Compensation and Efficiency Enhancements in Achromatic Meta-lenses

“…Integrated-resonant units (IRUs), associating various meta-atoms, resonant modes, and functionalities into one supercell, have been proposed to overcome this bottleneck, which provides additional degrees of freedom for controlling composite and multifunctional optical responses. , Considering the constituting materials, all-dielectric IRUs with high aspect ratios enable waveguide-like resonances with different orders . These resonances are mainly located inside the material and have a weak interaction with others, so the phase dispersion is mostly contributed by the propagation phase based on the effective refractive index and height of nanostructures.…”

“…16,17 Considering the constituting materials, all-dielectric IRUs with high aspect ratios enable waveguide-like resonances with different orders. 18 These resonances are mainly located inside the material and have a weak interaction with others, so the phase dispersion is mostly contributed by the propagation phase based on the effective refractive index and height of nanostructures. Plasmonic IRUs with external field distributions are beneficial for strong near-field interactions.…”

Varifocal Metalenses: Harnessing Polarization-Dependent Superposition for Continuous Focal Length Control

“…7−10 This miniaturization potential is particularly valuable in applications such as smartphone cameras, 11 augmented reality displays, 12,13 and medical imaging. 14 The design flexibility of metalenses 15 allows for customized optical properties tailored to specific applications such as edge-enhanced and functional imaging. 16−18 Via the precise tailoring of the geometry and arrangement of nanostructures, metalenses can exhibit unique characteristics, including achromatic behavior 19,20 and multifunctional focusing effects.…”

“…Metalenses can be fabricated on thin, flexible substrates, enabling easy integration into compact devices and overcoming the bulkiness associated with conventional lens systems. − This miniaturization potential is particularly valuable in applications such as smartphone cameras, augmented reality displays, , and medical imaging . The design flexibility of metalenses allows for customized optical properties tailored to specific applications such as edge-enhanced and functional imaging. − Via the precise tailoring of the geometry and arrangement of nanostructures, metalenses can exhibit unique characteristics, including achromatic behavior , and multifunctional focusing effects. , Furthermore, the concept of a varifocal metalens takes this design flexibility to the next level by incorporating active materials that respond to external stimuli. , When these stimuli are controlled, the varifocal metalenses can change their physical shape or effective refractive index of the surrounding environment, thereby dynamically altering their focal length.…”