Plasmonic Resonance toward Terahertz Perfect Absorbers

Withayachumnankul, Withawat; Shah, Charan M.; Ung, Benjamin S.-Y.; Padilla, Willie J.; Bhaskaran, Madhu; Abbott, Derek; Sriram, Sharath

doi:10.1021/ph500110t

Cited by 76 publications

(26 citation statements)

References 28 publications

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“…An example is the need for a perfect absorber of terahertz waves, which has applications effi cient narrowband perfect absorption with a plasmonic coaxial mode. [ 31 ] In this work, we show that distinctive plasmonic modes in silicon-based cavities can serve to greatly enhance the absorption bandwidth for ultrabroadband operation. Our single-layered structure is more attractive than prior broadband multilayered absorbers in terms of fabrication simplicity, cost, and allows for possible integration into silicon-based systems.…”

Section: Introductionmentioning

confidence: 78%

“…[ 30,31 ] Note that DRIE was performed using the Bosch process, where a mixture of SF6 (to etch silicon) and C4F8 (to passivate sidewalls to enable deep etching) gas was alternatively permitted into the high vacuum chamber and ionized by applying RF power. The etch rate of the silicon wafer using the Bosch DRIE process was approximately 0.4 µm per cycle, with process timed to etch 65-µm deep trenches into the doped silicon wafer.…”

Section: Full Paper Full Paper Full Papermentioning

confidence: 99%

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Ultrabroadband Plasmonic Absorber for Terahertz Waves

Cheng

Withayachumnankul

Upadhyay

et al. 2014

Advanced Optical Materials

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106

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in high-resolution terahertz imaging and detection for security and biomedicine.By defi nition, perfect absorbers can absorb EM waves with near-unity absorbance, which are promising for applications in terahertz imaging and detection via enhanced contrast and sensitivity. Metamaterials are candidates for creating perfect absorbers owing to the possibility of tailoring the response of the structure with great fl exibility. [ 5,6 ] Landy et al. [ 7 ] fi rst demonstrated the perfect metamaterial absorber concept in the microwave range, and since then great interest in EM absorbers has extended toward optical frequencies in recent years. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Metamaterial absorbers typically consist of two coupled metallic layers separated by a dielectric spacer to create electric and magnetic responses for impedance matching with free space. [ 23 ] The electric response can be obtained from excitation of the top metal layer readily coupled to an external electric fi eld, while the magnetic response is provided by pairing the top layer with a metal ground plane or metal wire for an external magnetic fi eld. In the microwave and terahertz regions, these metamaterial absorbers obtain high absorption through dielectric loss and impedance matching at resonance. [ 23 ] The absorption frequency range and amplitude can be tuned by adjusting the shape, size, thickness, and properties of the metallic structure and dielectric spacer. Due to the nature of resonance response, these metamaterial absorbers usually exhibit narrowband absorption that has advantages in applications such as fi ltering, sensing, and modulation. [ 24 ] Broadband perfect absorbers are desirable for other applications such as high-effi ciency signal detection and communications. This has necessitated signifi cant research effort toward extending the absorption bandwidth. A straightforward approach is to cluster multiple resonating structures with different sizes in each unit cell to create a number of absorption bands. [ 9,22 ] Graphene has been introduced to construct broadband terahertz absorbers due to its exceptional properties, such as optical transparency, fl exibility, and tunability. [25][26][27] However, the structure is demanding in terms of cost and complexity. Another alternative promising material for terahertz absorption is a moderately doped semiconductor, which can be readily fabricated using conventional micro-fabrication techniques. At terahertz frequencies, doped semiconductors have desirable conductive loss, enabling them to sustain surface plasmon polaritons (SPPs) and correspondingly localized surface plasmon resonances (LSPRs) via periodic structures. [28][29][30] Recently, we have demonstrated that doped silicon can be engineered to attain highly Perfect absorbers that exhibit broadband absorption of terahertz radiation are promising for applications in imaging and detection due to enhanced contrast and sensitivity in this relatively untapped frequency regime. Here, terahertz plasmonics is used ...

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Section: Introductionmentioning

confidence: 78%

Section: Full Paper Full Paper Full Papermentioning

confidence: 99%

Ultrabroadband Plasmonic Absorber for Terahertz Waves

Cheng

Withayachumnankul

Upadhyay

et al. 2014

Advanced Optical Materials

Self Cite

106

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“…On the other hand, lossy dielectric materials with moderately high relative permittivity are engineered to enhance coupling between and field confinement within subwavelength resonant cavity bodies. Such materials can also be designed to confined fields and subsequently dissipate in resonators for broadband terahertz absorbers …”

Section: Dielectric Materials As Resonant Elements and Structuresmentioning

confidence: 99%

“…Doped dielectric resonators, for example, doped Si, exhibit metallic behavior and support LSPRs in confined cavities or delocalized in‐plane SPP, on resonance. Examples of engineered dielectric material‐based resonator geometries include microcylindrical cavities, cylinders, cross‐shaped, disks, sawtooth, microspheres, etc., have been demonstrated for perfect absorption of terahertz radiation. Heavily doped Si has seen wide application in this respect due to ease of fabrication based on its crystallographic nature.…”

Section: Lossless Dielectric Materialsmentioning

confidence: 99%

Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques

Ako

Upadhyay

Withayachumnankul

et al. 2019

Advanced Optical Materials

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106

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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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“…On the line of scaling‐down, the research passed the challenges of sub‐mm waves and THz frequencies, one of the most difficult and unexplored domains in electromagnetics . In this range, metamaterials offer exciting opportunities for perfect absorbers, emitters, fibers, switches, modulators , also available with superconducting , or flexible implementations.…”

Section: Introductionmentioning

confidence: 99%

New degrees of freedom in nonlinear metamaterials

Lapine

2017

Phys. Status Solidi B

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This is an overview of the recent achievements in exploiting novel degrees of freedom in metamaterial design, which enable sophisticated nonlinear coupling mechanisms and bring enhancement to nonlinear behavior. One of the novel paradigms makes use of mechanical feedback, achieved by embedding electromagnetic resonators within elastic medium or engineering explicit elastic links between them, such as rotational feedback. These designs provide broad‐band self‐adjustable resonances, self‐oscillations, chaotic regimes, nonlinear chirality and, spontaneous chiral symmetry breaking. With this respect, a range of implementations has been analyzed, from flexible helices for microwaves to artificial electrostriction in optics. Another concept benefits from multi‐frequency operation, where the properties in completely distinct frequency ranges become entangled through specific metamaterial design –for example, direct optical coupling can be introduced between microwave resonators, providing an independent interaction channel. It was also found that hyperbolic metamaterials can bring notable benefits to classical nonlinear processes by imposing unusual phase matching solutions, with a rich choice of matching combinations. Finally, the boundary structure of metamaterials add yet another possibility to control their properties. Overall, the recent progress in these topics suggests a very positive outlook into the future of nonlinear metamaterials.

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Plasmonic Resonance toward Terahertz Perfect Absorbers

Cited by 76 publications

References 28 publications

Ultrabroadband Plasmonic Absorber for Terahertz Waves

Ultrabroadband Plasmonic Absorber for Terahertz Waves

Dielectrics for Terahertz Metasurfaces: Material Selection and Fabrication Techniques

New degrees of freedom in nonlinear metamaterials

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