3D Janus plasmonic helical nanoapertures for polarization-encrypted data storage

Abstract

Helical structures have attracted considerable attention due to their inherent optical chirality. Here, we report a unique type of 3D Janus plasmonic helical nanoaperture with direction-controlled polarization sensitivity, which is simply fabricated via the one-step grayscale focused ion beam milling method. Circular dichroism in transmission of as large as 0.72 is experimentally realized in the forward direction due to the spin-dependent mode coupling process inside the helical nanoaperture. However, in the backward direction, the nanoaperture acquires giant linear dichroism in transmission of up to 0.87. By encoding the Janus metasurface with the two nanoaperture enantiomers having specified rotation angles, direction-controlled polarization-encrypted data storage is demonstrated for the first time, where a binary quick-response code image is displayed in the forward direction under the circularly polarized incidence of a specified handedness, while a distinct grayscale image is revealed in the backward direction under linearly polarized illumination with a specified azimuthal angle. We envision that the proposed Janus helical nanoapertures will provide an appealing platform for a variety of applications, which will range from multifunctional polarization control, enantiomer sensing, data encryption and decryption to optical information processing.

Progresses in the practical metasurface for holography and lens

“…The study of metasurface holography has been carried out to increase the amount of information on one metasurface. This method is made possible by using a new structure, controlling the properties of incident light, or using a reflection space as modulating range with transmission space [21,[52][53][54][55][56][57][58][59]. The phase control via PB phase is well known to have a broadband characteristic [21,29,51].…”

“…This method enables vectorial holography, which can realize holography having the spatially varying polarization state and amplitude. In addition, as shown in Figure 4H, a plasmonic metasurface can be obtained by milling a metal plate while controlling the concentration of the focused ion beam [58,62]. The resultant meta-atom breaks mirror symmetry, which is not achievable with fixed height and planar meta-atom [95][96][97][98].…”

“…This leads to the chiral response to the circular polarization, and some studies employ this scheme to realize polarization-dependent image generation. The study shown in Figure 5F achieves polarization-controlled Janus image, by control of the extinction ratio of the amplitude by changing the incident light direction and polarization [58].…”

Tunable circular dichroism of chiral metamaterial based on phase transition of vanadium dioxide (VO2)

“…Many researches have been carried out to pursue a large circular dichroism from microwave to visible regions. Three-dimensional and planar chiral metamaterials such as helixshaped and L-shaped MMs [15,[19][20][21], bilayered structures [17,22,23], kirigami-based structures [24] and chiral oligomers [25,26] have been designed to study the effect of CD and other chiroptical responses. However, for most traditional metamaterials, CD responses are untunable as soon as the structures are fabricated, which limits their applications in programmable metamaterial, holography and electromagnetic phase modulations.…”

Intrinsic Chirality and Multispectral Spin‐Selective Transmission in Folded Eta‐Shaped Metamaterials

“…Compared with the weak chirality of the natural occurring media, elaborately tailored artificial chiral metamaterials consisting of subwavelength constituent elements offer an effective avenue for achieving engineered chirality . Chiral metamaterials exhibit orders of magnitude larger chiral optical effects than that of their naturally occurring counterparts, which makes chiral metamaterials highly promising candidates for various applications, including biodetection and chemical analysis, chiral light detector, broadband circular polarizer, chiral optical imaging, nonlinear optics, polarization‐encrypted data storage, and even negative refractive index materials . In the past decades, there have been some significant progresses on manipulating the polarization state of light by 2D and 3D metamaterials .…”