Non‐Interleaved Bilayer Complex‐Amplitude Janus Metasurface Enabling Energy‐Tailorable Bidirectional Wave Modulation

Abstract

Janus metasurfaces have attracted significant attention due to their key feature of asymmetric transmission in numerous practical applications, such as asymmetric data inscription in communications and dual side displays in smart mobile devices. More compact and integrated spatial wave modulation components call for implementations of non‐interleaved bilayer complex‐amplitude (CA) Janus metasurfaces. Here, by introducing composite geometry phase into propagation phase, direction‐dependent decoupling relation between amplitude and phase engineering is derived, and the mechanism of energy‐tailorable bidirectional wave modulation is elucidated via extremely simple single‐pixeled Janus elements. A non‐interleaved bilayer CA Janus metasurface is thus proposed. Bidirectional amplitude‐phase profiles with both‐transmission (T–T) or transmission–reflection‐integration (T–R) operational modes can readily be achieved. Numerical analysis and experimental verification of direction‐dependent energy allocation and reciprocal asymmetric holograms are performed to demonstrate the excellent manipulation accuracy and decorrelation under bidirectional illuminations. On this basis, a series of coplanar image syntheses, including frequency–polarization multitasking and T–R dual‐channel multiplexing, based on the proposed bidirectional CA modulation mechanism are experimentally demonstrated in the microwave region. This asymmetric transmission mechanism will promote developments of Janus metasurfaces for multichannel processing and information multiplexing applications in miniaturized and highly integrated systems.

Matrix Diffractive Deep Neural Networks Merging Polarization into Meta‐Devices

“…[ 48 ] However, the interleaved metasurface, whose period of the unit cell is about one working wavelength, operates at high‐order diffraction mode, resulting in reduced spatial resolution, complex detection configuration, and low hologram efficiency. [ 50–52 ] To address these issues, we demonstrate that with the assistance of proposed M‐D 2 NN, non‐interleaved birefringent meta‐atoms, with less modulation degrees of freedom, can be used to realize Jones matrix eight‐channel modulation. Here, we transfer the goal from optimizing the Jones matrix of the meta‐atoms to optimizing the Jones matrix of the overall meta‐device to take advantage of the superposition and optimization of polarized EM waves during the spatial propagation process.…”

3D Reconfigurable Vectorial Holography via a Dual‐Layer Hybrid Metasurface Device

“…Each neuron in the output layer represents the Jones vector of VMH in the desired plane and the output matrix U VMH has the same form as U input , as depicted in Equation (2) . The connection between layers is formulated through the Rayleigh-Sommerfeld diffraction theory, [61] which reads…”

“…Holography, as an intriguing technique for reconstructing the 3D light field of an object, has penetrated all areas of society in recent years and is extensively utilized in modern scientific research and industrial production, especially in modern detection, bioengineering, medicine, security, and storage technology. [1][2][3][4][5][6] Recently, metasurface-based holography has revolutionized conventional holography, consisting of the subwavelength-spaced arrays of meta-atoms that can manipulate the properties of electromagnetic (EM) waves point by point allowing the unrestrained possibility. [7][8][9][10][11][12] Among them, vectorial metasurface holography (VMH) [13,14] not only controls the complex-amplitude distribution of the holographic image but also arbitrarily customizes its polarization distribution.…”

Direction-Duplex Janus Metasurface for Full-Space Electromagnetic Wave Manipulation and Holography

“…To overcome the above problem, the concept of “Janus metasurface” is proposed to mimic the two-faced god in Roman mythology that enables a single metasurface to integrate one functionality for a wave propagating along one direction but a totally different one for the opposite direction with the same incident polarization, for example, projecting distinct free-space holographic images for incidences with an opposite propagation direction. , The underlying mechanism is to induce asymmetric transmission behavior by chiral structures and their intrinsic giant chiral properties − from judiciously designed asymmetric spatial configurations. Due to the promising perspective of Janus metasurfaces in miniaturized and highly integrated multifunctional systems, extensive efforts have been devoted to exploring new design methods, extending overall channels, and enhancing performances, ,− such as segmented metasurfaces for transmission and reflection controls, composite geometry phase and propagation phase metasurface for energy-tailorable wave modulation, frequency-multiplexed metasurface for transmission control at distinct frequencies, etc. Despite these progresses, there are still some problems that should be overcome to fully exploit the Janus metasurface for high-integrated wave manipulations.…”