Dual‐Polarized Tri‐Channel Encrypted Holography Based on Geometric Phase Metasurface

Abstract

Metasurface-based encrypted holography has drawn much attention recently due to its excellent ability in storing/displaying information with good security. To enhance the encryption security of metasurface holograms, multiplexing techniques, for which a large number of parameters need to be scanned to achieve the desired meta-atoms, are highly demanded. Herein, a metasurface design scheme, which utilizes solely geometric phase elements to manipulate both co-and cross-polarized reflected fields independently, is proposed. Using an improved weighted Gerchberg-Saxton (GSW), a holographic algorithm is proposed for 1-bit phase, dual-polarized tri-channel encrypted metamirrors. Proofof-concept prototypes are fabricated and experimental demonstrations are performed at microwave frequencies. Simulations and measurements are carried out to validate the proposed design, and the results agree well with the theoretical design scheme. Such dual-polarized and tri-channel encrypted metamirrors are appealing for applications in polarimetric imaging, information encryption/ storage and beam splitting, shaping and steering.

Metasurface Holography in the Microwave Regime

“…The proposed metamirror provides a high-performance solution for low-cost and lightweight beam-shaping and beam-focusing devices [100]. Additionally, as presented in Figure 4b, dual-polarized tri-channel encrypted holography is realized by a PB phase reflective metasurface when it is illuminated by an LP incident plane wave, which is appealing for applications in information encryption/storage [101]. In order to overcome the bulky profile due to the plane wave illumination, a low-profile holographic method was proposed using a leaky-type 2-bit coding Fabry-Perot metasurface with inplane feeding in the microwave domain.…”

Angular‐Encrypted Quad‐Fold Display of Nanoprinting and Meta‐Holography for Optical Information Storage

“…During the past decade, the invention of metasurface has created a promising device platform to boost information density and encryption. [1][2][3][4][5][6][7][8] Featured with virtually two-dimensional planar surfaces and artificial subwavelength-scale nano-textured patterns, metasurfaces have been studied and demonstrated independent-encoded holographic and nanoprinting images. By strategically screening the architectural blocks to produce the angular-encrypted complex-amplitude arrangement, we have successfully enabled the quad-channel multiplexing, including two angular-encrypted meta-holography and two simultaneous nanoprintings within a single metasurface design.…”

“…During the past decade, the invention of metasurface has created a promising device platform to boost information density and encryption. [ 1–8 ] Featured with virtually two‐dimensional planar surfaces and artificial subwavelength‐scale nano‐textured patterns, metasurfaces have been studied and demonstrated to control light waves across the entire spectral range and enable various optical applications and functionalities, including optical cloaking, [ 9,10 ] plasmonic coloring, [ 11 ] wavefront shaping, [ 12–15 ] meta‐lenses, [ 16,17 ] meta‐holography, [ 18–23 ] etc.…”

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to control light waves across the entire spectral range and enable various optical applications and functionalities, including optical cloaking, [9,10] plasmonic coloring, [11] wavefront shaping, [12][13][14][15] meta-lenses, [16,17] meta-holography, [18][19][20][21][22][23] etc.Due to its compact scale and programmable versatility, more recent endeavors on metasurface have demonstrated to make it a competitive candidate for optical information encryption and storage. [1][2][3][4][5][6][7][8] For instance, by encoding the spectral amplitude/phase response, nanoprinting [24,25] /holography [18][19][20][21][22][23] graphs and encryption have been created to exhibit high-resolution displays, which are attainable under microscopes or projected on an optical screen. Other attempts have also been made to successfully enable the simultaneous multiplexing channels of both nanoprinting and metaholography.

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Terahertz Near‐Field Vortex Beams with Variable Intensity Profiles Based on Geometric Metasurfaces

“…By carefully designing the orientation of each anisotropic meta-atom, the required phase profile can be produced by a geometric metasurface, enabling the control of the wavefront of EM waves. Recent works regarding geometric metasurface such as generalized Snell's law [14][15][16], holograms [17][18][19][20][21][22][23][24], metalens [25][26][27][28][29][30][31][32][33][34], spin Hall effect [35][36][37][38], polarization convertors [39][40][41][42][43], and nonlinear photonics [44][45][46][47] have sufficiently proven its outstanding capabilities in EM wave manipulation. Moreover, the generations of vortex beams [48][49][50][51][52], vector vortex beams [53,54] and perfect vortex beams [55][56][57] have been demonstrated using geometric metasurface approach.…”