All-optical active THz metasurfaces for ultrafast polarization switching and dynamic beam splitting

Cong, Longqing; Srivastava, Yogesh Kumar; Zhang, Huifang; Zhang, Xueqian; Han, Jiaguang; Singh, Ranjan

doi:10.1038/s41377-018-0024-y

Cited by 211 publications

(121 citation statements)

References 52 publications

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“…For the polarization control, the broadband quarter‐wave conversion has seldom been reported. Narrowband quarter‐wave conversion is already challenging in the THz range, as LC phase shifters need a sufficient cell depth and metamaterials have a limited accuracy . Using the Fabry–Perot effect or anisotropic reflection extends the bandwidth to no more than 0.7 THz, which is still less than a half of this work.…”

Section: Resultsmentioning

confidence: 99%

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Highly Efficient Ultra‐Broadband Terahertz Modulation Using Bidirectional Switching of Liquid Crystals

Chen

Zhang

et al. 2019

Advanced Optical Materials

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Accurately manipulating field strength and polarization state are essential in various terahertz applications. Such manipulations are based on the efficient modulation of the amplitude and phase of electromagnetic waves. However, there is a lack of such terahertz modulators with sufficient efficiency and bandwidth. Herein, the Brewster–critical angle is exploited for modulation by using a nematic liquid crystal. Unlike liquid crystal phase shifters that only give a narrowband phase delay via a one‐directional switch, the presented device modulates both the amplitude and phase across an ultra‐broadbandwidth via a bidirectional active switch. An average intensity modulation depth over 99.6% is achieved for 0.2–1.6 THz. Furthermore, highly accurate polarization conversion between linear and circular states is also realized for 0.4–1.8 THz, with the average degree of linear and circular polarizations as high as 0.994 and 0.998, respectively. The superior accuracy, bandwidth, and active control achieved provide great potential for multifunctional terahertz modulation.

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Section: Resultsmentioning

confidence: 99%

“…The Goos–Hänchen shift can be utilized for achieving frequency‐dependent dispersion . Metamaterials are still a popular candidate for narrowband polarization switching . Stacked metallic gratings were implemented to relatively extend the working bandwidth, which is still limited due to the Fabry–Perot effect.…”

Section: Introductionmentioning

confidence: 99%

Highly Efficient Ultra‐Broadband Terahertz Modulation Using Bidirectional Switching of Liquid Crystals

Chen

Zhang

et al. 2019

Advanced Optical Materials

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“…These devices have either been demonstrated as freestanding devices or devices supported on a ground plane . With a suitable dielectric material and shape of the resonating element, a wide range of applications can be demonstrated based on the manipulation of polarization, phase, and amplitude of an incident electric field. Device demonstration examples include band‐pass transmission; broad‐ and narrow‐band absorbers for detection applications; low‐loss polarizers; low‐loss and high‐gain beamforming; or devices demonstrating dynamic properties such as modulators and switches …”

Section: Dielectric Materials As Spacers and Substrates At Terahertz mentioning

confidence: 99%

Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques

Ako

Upadhyay

Withayachumnankul

et al. 2019

Advanced Optical Materials

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on distinctive spectral signatures resulting from vibrational modes of covalent and hydrogen bonds. [8,[13][14][15][16] The focus on this spectrally rich region is attributed to the highly coherent and nonionizing nature of terahertz radiation, wide unallocated frequency bands, distinctive wavelengths, and their penetration through a significant depth of dielectric materials. Terahertz technology is geared toward realizing devices that can efficiently manipulate the phase, amplitude, and polarization of terahertz radiations for the above-mentioned myriad of applications.However, progress in this domain is held back by low terahertz power available from compact sources, high free-space path loss, and limited choice of materials that exhibit less absorption of terahertz waves. [17] Owing to the fact that natural materials demonstrate weak wave-matter interaction at terahertz frequencies, terahertz devices with engineered subwavelength resonant metallic inclusions on dielectric spacers have been realized, to interact strongly with an incident electromagnetic wave.In the past, metamaterials have been a promising route to building terahertz devices. These devices have in essence been engineered as 3D resonating elements that effectively manipulate both permittivity and permeability of an effective medium to couple to free space. The underlining disadvantage of these structures is the difficulty involved in the fabrication of 3D geometrical structures using standard semiconductor fabrication techniques. Standard fabrication techniques are generally amenable to 2D design with extrusion of these structures into thickness (the third, vertical dimension). Moreover, the choice and availability of dielectric materials and metals that provide sufficient interaction while retaining device efficiency has proved challenging. [13,[18][19][20] Recently, effective manipulation of electromagnetic wave has been widely demonstrated with 2D metasurfaces, which were originally employed as building blocks for 3D metamaterials. In these lower-dimension designs, effective manipulation of terahertz waves for various applications is achieved by carefully designing sub-wavelength resonant structures as is evident in published review articles. [21,22] Metasurfaces present high degree of compactness that enhances radiation efficiency. Additionally, the planar form factor of metasurfaces enables Manipulation of terahertz radiation opens new opportunities that underpin application areas in communication, security, material sensing, and characterization. Metasurfaces employed for terahertz manipulation of phase, amplitude, or polarization of terahertz waves have limitations in radiation efficiency which is attributed to losses in the materials constituting the devices. Metallic resonators-based terahertz devices suffer from high ohmic losses, while dielectric substrates and spacers with high relative permittivity and loss tangent also reduce bandwidth and efficiency. To overcome these issues, a proper choice of low loss and low relative permittivi...

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“…Composed of two-dimensional plasmonic or dielectric phasecontrol elements, metasurfaces provide a flat and ultracompact platform for flexible wavefront engineering [11][12][13]. Metasurface applications include anomalous refraction/reflection [14][15][16][17][18], lensing [19][20][21][22], special beam generation [23][24][25], surface plasmon coupling [26][27][28], etc. Some functionalities of metasurfaces can even go beyond those of conventional optical elements.…”

Section: Introductionmentioning

confidence: 99%

Direct polarization measurement using a multiplexed Pancharatnam–Berry metahologram

Zhang

Yang²,

Yue

et al. 2019

Optica

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108

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Polarization, which represents the vector nature of electromagnetic waves, plays a fundamental role in optics. Fast, simple, and broadband polarization state characterization is required by applications such as polarization communication, polarimetry, and remote sensing. However, conventional polarization detection methods face great difficulty in determining the phase difference between orthogonal polarization states and often require a series of measurements. Here, we demonstrate how polarization-dependent holography enables direct polarization detection in a single measurement. Using a multiplexed Pancharatnam-Berry phase metasurface, we generate orthogonally polarized holograms that partially overlap with a spatially varying phase difference. Both amplitude and phase difference can be read from the holographic image in the circular polarization basis, facilitating the extraction of all Stokes parameters for polarized light. The metahologram detects polarization reliably at several near-infrared to visible wavelengths, and simulations predict broadband operation in the 580-940 nm spectral range. This method enables fast and compact polarization analyzing devices, e.g., for spectroscopy, sensing, and communications.

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All-optical active THz metasurfaces for ultrafast polarization switching and dynamic beam splitting

Cited by 211 publications

References 52 publications

Highly Efficient Ultra‐Broadband Terahertz Modulation Using Bidirectional Switching of Liquid Crystals

Highly Efficient Ultra‐Broadband Terahertz Modulation Using Bidirectional Switching of Liquid Crystals

Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques

Direct polarization measurement using a multiplexed Pancharatnam–Berry metahologram

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