Recent Progress in Terahertz Metasurfaces

Al-Naib, Ibraheem; Withayachumnankul, Withawat

doi:10.1007/s10762-017-0381-2

Cited by 72 publications

(34 citation statements)

References 56 publications

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“…165 A metasurface is simply a planar or quasi-planar version of a metamaterial, a single quasi-2D portion of a metamaterial's volume. 166,167 As such, there is no substantive difference between a passive array and a nonuniform metasurface designed for beam control, aside from a tendency for the latter to make use of more deeply subwavelength cells. In this article, however, the terminology of "reflectarrays" and "transmitarrays" is adopted, as the initial demonstration of reflectarray antennas precedes the advent of metamaterials by several decades.…”

Section: Reflectarrays and Transmitarraysmentioning

confidence: 99%

Tutorial: Terahertz beamforming, from concepts to realizations

et al. 2018

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The terahertz range possesses significant untapped potential for applications including high-volume wireless communications, noninvasive medical imaging, sensing, and safe security screening. However, due to the unique characteristics and constraints of terahertz waves, the vast majority of these applications are entirely dependent upon the availability of beam control techniques. Thus, the development of advanced terahertz-range beam control techniques yields a range of useful and unparalleled applications. This article provides an overview and tutorial on terahertz beam control. The underlying principles of wavefront engineering include array antenna theory and diffraction optics, which are drawn from the neighboring microwave and optical regimes, respectively. As both principles are applicable across the electromagnetic spectrum, they are reconciled in this overview. This provides a useful foundation for investigations into beam control in the terahertz range, which lies between microwaves and infrared light. Thereafter, noteworthy experimental demonstrations of beam control in the terahertz range are discussed, and these include geometric optics, phased array devices, leaky-wave antennas, reflectarrays, and transmitarrays. These techniques are compared and contrasted for their suitability in applications of terahertz waves.

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Section: Reflectarrays and Transmitarraysmentioning

confidence: 99%

Tutorial: Terahertz beamforming, from concepts to realizations

et al. 2018

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“…Though Drude‐type materials, such as noble metals and heavily doped semiconductors, exhibit high ohmic losses at terahertz frequencies, a focus is still placed at realizing terahertz resonators with these materials in combination with dielectric spacers due to ease of fabrication with standard microfabrication techniques and acceptable efficiency . The electromagnetic response of these devices when excited by an external electric field is dependent on the conduction current on the metallic resonators and significantly on the degree of field confinement in the spacers carrying these resonators.…”

Section: Dielectric Materials As Spacers and Substrates At Terahertz mentioning

confidence: 99%

“…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 . Metasurfaces present high degree of compactness that enhances radiation efficiency.…”

Section: Introductionmentioning

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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“…Currently, terahertz time-domain spectroscopy (THz TDS) and imaging techniques are applied in various fields such as astronomy, security screening, communications, genetic engineering, pharmaceutical quality control, medical imaging and biomedical engineering [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Study of glucose concentration influence on blood optical properties in THz frequency range

Gusev¹,

Demchenko²,

Litvinov³

et al. 2018

Nanosystems: Phys. Chem. Math.

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The optical properties of whole human blood with the different glucose level were studied by terahertz time-domain spectroscopy at frequencies ranging from 0.3 -0.5 THz. The increasing of refractive index of blood at the glucose level growth was shown for series of experiments. The dispersion of complex refractive index of human nails was obtained. Based on these data, the non-invasive glucose measuring technique was proposed which utilizes the reflection of the THz pulse from nail plate/nail bed interface.

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Recent Progress in Terahertz Metasurfaces

Cited by 72 publications

References 56 publications

Tutorial: Terahertz beamforming, from concepts to realizations

Tutorial: Terahertz beamforming, from concepts to realizations

Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques

Study of glucose concentration influence on blood optical properties in THz frequency range

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