Stepwise Dual‐Fabry–Pérot Nanocavity for Grayscale Imaging Encryption/Concealment with Holographic Multiplexing

Abstract

the interference effect from lossy Fabry− Pérot (FP) cavity, which achieves perfect absorption, [8,9] colorful transmission [10][11][12] and could be integrated into functional optic devices. [13][14][15][16][17][18] By tuning the core insulator thickness, such MIM cavity offers the customizability for operation wavelength. Comparing to the traditional lossless FP cavity, [19,20] the MIM nanocavity utilizes the boundary lossy characteristics, thus enabling destructive interference for perfect absorption. [21] The simple film stack provides cost-effective and large-area fabrication with satisfactory optical performance in comparison to the counterpart of complex-shaped photonic nanoresonators. [22][23][24] Despite the highlight of revealing different coloring for nanoprinting application, [25][26][27][28] such triple-layered nanocavity lacks the ability to bring in multiple intensity stepwise for grayscale imaging exhibition. When it comes to the grayscale imaging demand for continuous intensity modulation, the MIM nanocavity cannot perform but instead dramatically change its reflection intensity from zero to unity within only ≈30 nm cavity thickness change. Moreover, MIM stack has seldom been demonstrated with multiplexing functionality for both near-field nanoprinting and holographic imaging due to its close correlation and mutual dependence between its reflection intensity and phase shift.Here, we propose a stepwise design for dual-Fabry-Pérot (DFP) nanocavity constructed by multilayer metal-insulatormetal-insulator-metal (MIMIM) to achieve grayscale imaging encryption/concealment with holographic multiplexing functionality. By stacking DFP cavities with controlling each cavity thickness, we enable that the reflected intensity and resonant wavelength (coloring) could simultaneously be modulated. Specifically, the dimension of top FP cavity determines its operation wavelength, while the bottom FP cavity determines the reflection grayscale intensity. Our proposed DFP scheme is theoretically and experimentally demonstrated to enable encrypt or conceal a meticulous grayscale image via making stepwise DFP patterns, as shown in Figure 1.

Immersive Tuning the Guided Waves for Multifunctional On‐Chip Metaoptics

“…For instance, metaholography is an emerging and universal strategy based on engineered nanoantennas array to construct an optical-field image. Beyond the freespace holography, [12][13][14][15][16] the creation of on-chip metasurface enjoys numerous unique advantages, such as zero-order diffraction elimination, capability for multiple cascading, [17] alignment free, [18] and compatibility with other miniature on-chip elements. [19] However, as emerging on-chip elements, most previous studies of on-chip metasurface were restricted as passive with limited multiplexing capacity.…”

Metasurface‐Assisted Optical Encryption Carrying Camouflaged Information

“…Metasurface is an artificially planar‐structure material that has the superior capability of controlling DOF of light at subwavelength scale, [ 1–8 ] leading to a series of novel optical encryption technologies. [ 9–20 ] For nanoprinting, [ 21–24 ] these DOFs offer the possibility of encoding multiple meta‐images into different optical dimensions, thus improving the security and capacity of optical encryption. By modulating geometric dimension of single‐celled nanostructures in two orthogonal directions, two color meta‐images can be encoded with different polarization light.…”

“…Owing to the abundant degrees of freedom (DOF) of light (e.g., amplitude, phase, polarization, and frequency), optical encryption technology has significant advantages of multi-dimensionality, large capacity, high design freedom, and high security.Metasurface is an artificially planarstructure material that has the superior capability of controlling DOF of light at subwavelength scale, [1][2][3][4][5][6][7][8] leading to a series of novel optical encryption technologies. [9][10][11][12][13][14][15][16][17][18][19][20] For nanoprinting, [21][22][23][24] these DOFs offer the possibility of encoding multiple meta-images into different optical dimensions, thus improving the security and capacity of optical encryption. By modulating geometric dimension of single-celled nanostructures in two orthogonal directions, two color meta-images can be encoded with different polarization light.…”

Dynamic Augmented Reality Display by Layer‐Folded Metasurface via Electrical‐Driven Liquid Crystal

“…The invention of metasurfaces creates new degrees of freedom to control light at the subwavelength resolution and emerges as a promising platform for novel optical meta‐devices and meta‐systems. Various fascinating functionalities have been achieved by single‐layer metasurface design, including perfect absorber, [ 1,2 ] nanoprinting display, [ 3–5 ] beam steering, [ 6,7 ] metalens, [ 8,9 ] meta‐holography, [ 10–18 ] and many others. [ 19,20 ] However, heading toward the development and achievement of more powerful meta‐devices and even more complicated meta‐systems, it inevitably demands the cascading and coupling between multi‐layer metasurfaces as a feasible design strategy.…”

“…absorber, [1,2] nanoprinting display, [3][4][5] beam steering, [6,7] metalens, [8,9] metaholography, [10][11][12][13][14][15][16][17][18] and many others. [19,20] However, heading toward the development and achievement of more powerful meta-devices and even more complicated meta-systems, it inevitably demands the cascading and coupling between multilayer metasurfaces as a feasible design strategy.…”