Doped polymer for low-loss dielectric material in the terahertz range

Headland, Daniel; Thurgood, Peter; Stavrevski, Daniel; Withayachumnankul, Withawat; Abbott, Derek; Bhaskaran, Madhu; Sriram, Sharath

doi:10.1364/ome.5.001373

Cited by 26 publications

(13 citation statements)

References 34 publications

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“…From the perspective of an electromagnetic wave, such a structure is experienced as a homogeneous material with properties that are dependent on the structure and potentially different from those of the constituent materials. 88,89 For instance, an array of subwavelength air-holes in a given dielectric material will produce an effective medium that an electromagnetic wave experiences as an artificial dielectric, with an effective refractive index that lies between that of the bulk dielectric and air. This index depends on the hole radius and hole density, and hence it can be controlled by varying the size of the holes with respect to position.…”

Section: B Artificial Dielectricsmentioning

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: B Artificial Dielectricsmentioning

confidence: 99%

Tutorial: Terahertz beamforming, from concepts to realizations

et al. 2018

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“…Curing of PDMS can be done in a preheated oven or hot plate at 100 °C for 15 min or left naturally in an ambient condition for greater than 24 h. Freestanding PDMS‐based devices can be released easily when spun on aluminum thin film‐coated silicon wafer . In one demonstration, PDMS nanocomposites with alumina nanoparticles or polytetrafluoroethylene (PTFE) inclusions are shown to exhibit a slightly lower dissipation than that of bare PDMS . However, PDMS harbors some challenges due to its highly hydrophobic surface.…”

Section: Fabrication Of Single and Multilayer Terahertz Metasurface Dmentioning

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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“…The middle layer is 27 µm thick, and composed of low loss cyclo‐olefin copolymer (COC) which has a relative permittivity of ε r = 2.34 and loss tangent tan δ = 0.0007. This dielectric material used as a spacer has lower dielectric loss compared to polydimethylsiloxane and other polymers with tan δ = 0.06 used in the base half‐wave mirror designed by Cheng et al In order to avoid grating lobes, the unit cell size is chosen to be 120 µm, which is less than the shortest operating wavelength of 200 µm at 1.50 THz. The ground plane is a gold layer with a thickness of 200 nm.…”

Section: Designmentioning

confidence: 99%

Broadband Terahertz Circular‐Polarization Beam Splitter

Lee

Nirantar

Headland

et al. 2017

Advanced Optical Materials

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to each other. However, drawbacks of these conventional polarization-sensitive devices include narrow operation bandwidth, high cost, low efficiency, and bulkiness. In the terahertz region, an additional issue is related to material availability, since few natural materials exhibit strong birefringence with low loss. [4,5] Circularly polarized terahertz waves are important for studying chiral structures as many molecules in biology and chemistry are chiral and respond differently to left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) waves. [13] In addition, circular polarization can increase channel capacity in wireless communications. As an alternative, metasurfaces can provide designable birefringence at desirable frequencies, among other properties not commonly found in nature. [14] For example, dielectric chiral structures made of silicon [15] and titanium dioxide nanofin gratings [16] capable of circular-polarization beam splitting have been demonstrated at optical frequencies. Aside from that, metal nanoantennas [17] at the mid-infrared range and rotated microstrip patches [18] at microwave frequencies have also been demonstrated with a similar concept. Likewise, dual-image holograms can be generated because of different responses to LHCP and RHCP waves. [19][20][21] However, many of these existing designs are either inherently lossy, complicated, and/or narrowband. At terahertz frequencies, there are, to date, no existing metasurface designs capable of circular-polarization beam splitting.In this paper, we experimentally demonstrate an ultrathin broadband and efficient reflective beam splitter for circular polarization operating at the terahertz band. Relying on the concepts of birefringent metamaterials and localized phase control, the structure employs metallic planar coaxial disk-ring resonators over a ground plane as phase-shifting elements. Each element offers three neighboring resonances that altogether provide a half-wave-mirror response over a large bandwidth. A proper relative orientation between the cells results in a linear phase ramp with a positive or negative phase trend depending on the handedness of circular polarization. Effectively, this metasurface operates to deflect incident LHCP or RHCP waves into opposite sides with predetermined angles away from specular reflection. The design is characterized using a conventional terahertz time-domain spectroscopy (THz-TDS) system.

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Doped polymer for low-loss dielectric material in the terahertz range

Cited by 26 publications

References 34 publications

Tutorial: Terahertz beamforming, from concepts to realizations

Tutorial: Terahertz beamforming, from concepts to realizations

Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques

Broadband Terahertz Circular‐Polarization Beam Splitter

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