Optical properties of metasurfaces infiltrated with liquid crystals

Lininger, Andrew; Zhu, Alexander Y.; Park, Joon-Suh; Palermo, Giovanna; Chatterjee, Sharmistha; Boyd, J.R.; Capasso, Federico; Strangi, Giuseppe

doi:10.1073/pnas.2006336117

Cited by 72 publications

(61 citation statements)

References 42 publications

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“…To realize an electrically tunable bifocal metalens, an LC cell was combined with the metalens. To precisely control the polarization of the incident light using the LCs, rather than infiltrating the metalens with the LCs [ 32 ] we chose to combine the LC cell and metalens substrate in a sequential manner. The sandwich‐cell type LC cell consists of 4‐Cyano‐4′‐pentylbiphenyl (5CB) where the LC molecules are tangentially aligned to the substrate along the rubbing direction.…”

Section: Resultsmentioning

confidence: 99%

Electrically Tunable Bifocal Metalens with Diffraction‐Limited Focusing and Imaging at Visible Wavelengths

et al. 2021

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Tunable optical devices powered by metasurfaces provide a new path for functional planar optics. In particular, lenses with tunable focal lengths can play a key role in various fields with applications in imaging, displays, and augmented and virtual reality devices. Here, the authors demonstrate an electrically controllable bifocal metalens at visible wavelengths by incorporating a metasurface designed to focus light at two different focal lengths, with liquid crystals to actively manipulate the focal length of the metalens through the application of an external bias. By utilizing hydrogenated amorphous silicon that is optimized to provide an extremely low extinction coefficient in the visible regime, the metalens is highly efficient with measured focusing efficiencies of around 44%. They numerically design and experimentally realize and characterize tunable focusing and demonstrate electrically tunable active imaging at visible wavelengths using the bifocal metalens combined with liquid crystals. Diffraction limited focusing and imaging is verified through the analysis of the measured optical intensities at the focal points and the modulation transfer function. The bifocal metalens is used to demonstrate electrically modulated focus switching between the two designed focal planes, to display images of positive and negative target objects.

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Section: Resultsmentioning

confidence: 99%

Electrically Tunable Bifocal Metalens with Diffraction‐Limited Focusing and Imaging at Visible Wavelengths

et al. 2021

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“…Tuning and Reconfiguration of the HN-CPC and Polarization Switching LC-based photonic crystals, whether in 1D (CLC) or 3D (bluephase liquid crystals), are well known for tunability owing to the availability of a large assortment of liquid crystals with specially designed physical properties to suit application throughout a very wide spectral regime from visible to near infrared. The wavelength locations of photonic bandgap and band-edges and the dispersion characteristics and related optical properties of CLCs (e.g., spectral dependence of polarization rotation) can all be tailored-made through synthesis or electrically tuned by virtue of the easy susceptibilities of the LC constituents to external stimuli (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34).…”

Section: Polarization Rotation Of Complex Vector Fields Of Cw and Femtosecond-pulsed Lasersmentioning

confidence: 99%

“…Polarization rotation is independent of input polarization orientation and acts equally well on simple or complex vector fields (18)(19)(20)(21)(22) of continuous-wave (CW) or ultrafast pulsed laser beams. Liquid crystal-based CPCs also allow dynamic polarization switching and control by virtue of field-induced index/birefringence changing mechanisms at modest or ultrafast (picosecond to femtosecond) speeds (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34).…”

mentioning

confidence: 99%

Optical vector field rotation and switching with near-unity transmission by fully developed chiral photonic crystals

Chen

Khoo

2021

Proc. Natl. Acad. Sci. U.S.A.

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State-of-the-art nanostructured chiral photonic crystals (CPCs), metamaterials, and metasurfaces have shown giant optical rotatory power but are generally passive and beset with large optical losses and with inadequate performance due to limited size/interaction length and narrow operation bandwidth. In this work, we demonstrate by detailed theoretical modeling and experiments that a fully developed CPC, one for which the number of unit cells N is high enough that it acquires the full potentials of an ideal (N → ∞) crystal, will overcome the aforementioned limitations, leading to a new generation of versatile high-performance polarization manipulation optics. Such high-N CPCs are realized by field-assisted self-assembly of cholesteric liquid crystals to unprecedented thicknesses not possible with any other means. Characterization studies show that high-N CPCs exhibit broad transmission maxima accompanied by giant rotatory power, thereby enabling large (>π) polarization rotation with near-unity transmission over a large operation bandwidth. Polarization rotation is demonstrated to be independent of input polarization orientation and applies equally well on continuous-wave or ultrafast (picosecond to femtosecond) pulsed lasers of simple or complex (radial, azimuthal) vector fields. Liquid crystal–based CPCs also allow very wide tuning of the operation spectral range and dynamic polarization switching and control possibilities by virtue of several stimuli-induced index or birefringence changing mechanisms.

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“…As the voltage gradually changes, the nematic LCs (NLCs) platform is available to control the polarization state of the outgoing light [20]. Thus, the combination of LCs and metasurfaces can provide additional design ideas for active light modulation applications [21].…”

Section: Introductionmentioning

confidence: 99%

Electrically Tunable All-Dielectric Metasurfaces Integrated With Nematic Liquid Crystals for Information Encryption

Shen

Sun

et al. 2021

IEEE Photonics J.

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As artificially designed two-dimensional (2D) arrays of subwavelength nanostructures, metasurfaces provide a new avenue for the design of static planar optics. However, one would prefer a dynamic modulation of the metasurface in the event of practical applications. As a potentially important technique for information security, meta-holographic encryption has the characteristics of subwavelength pixels, precise control, and high safety factor. In this paper, by integrating birefringent liquid crystals (LCs) with all-dielectric metasurfaces in combination with visual cryptography (VC), we demonstrate a tunable metasurface with an information encryption function in the visible range. In the encryption process, the secret image is hidden in a set of unidentifiable and orthogonal arranged phase-only meta-holograms with high security of concealment. In the decryption process, the generated meta-hologram is illuminated by a plane wave and an electric field across the LC layer is applied to superimpose the reconstructed holographic patterns, thus we could acquire the secret image. Therefore, the decryption method can be flexibly and sufficiently adjusted with applied field under monitorable condition. For this reason, it is useful in enhancing the diversity of information hiding methods and improving the security of information. Our method can be extended to other similar applications.

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Optical properties of metasurfaces infiltrated with liquid crystals

Cited by 72 publications

References 42 publications

Electrically Tunable Bifocal Metalens with Diffraction‐Limited Focusing and Imaging at Visible Wavelengths

Electrically Tunable Bifocal Metalens with Diffraction‐Limited Focusing and Imaging at Visible Wavelengths

Optical vector field rotation and switching with near-unity transmission by fully developed chiral photonic crystals

Electrically Tunable All-Dielectric Metasurfaces Integrated With Nematic Liquid Crystals for Information Encryption

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