Abstract-Manifestation of kinetic-inductance in spectrally-narrow terahertz plasmon resonances in thin-film Cd3As2

Ashish Chanana, Neda Loftizadeh, Hugo O. Condori Quispe, Prashanth Gopalan, Joshua R. Winger, Steve Blair, Ajay Nahata, Vikram Deshpande, Michael A. Scarpulla, Berardi Sensale-Rodriquez,

https://arxiv.org/abs/1811.04306

Three-dimensional (3D) semimetals have been predicted and demonstrated to have a wide variety of interesting properties associated with its linear energy dispersion. In analogy to two-dimensional (2D) Dirac semimetals, such as graphene, Cd3As2, a 3D semimetal, has shown ultra-high mobility, large Fermi velocity, and has been hypothesized to support plasmons at terahertz frequencies. In this work, we demonstrate synthesis of high-quality large-area Cd3As2 thin-films through thermal evaporation as well as the experimental realization of plasmonic structures consisting of periodic arrays of Cd3As2 stripes. These arrays exhibit sharp resonances at terahertz frequencies with associated quality-factors (Q) as high as ~ 3.7. Such spectrally-narrow resonances can be understood on the basis of a large kinetic-inductance, resulting from a long momentum scattering time, which in our films can approach ~1 ps at room-temperature. Moreover, we demonstrate an ultrafast tunable response through excitation of photo-induced carriers in optical pump / terahertz probe experiments. Our results evidence that the intrinsic 3D nature of Cd3As2 provides for a very robust platform for terahertz plasmonic applications. Overall, our observations pave a way for the development of myriad terahertz (opto) electronic devices based on Cd3As2 and other 3D Dirac semimetals, benefiting from strong coupling of terahertz radiation, ultrafast transient response, magneto-plasmon properties, etc. Moreover, the long momentum scattering time, thus large kinetic inductance in Cd3As2, also holds enormous potential for the re-design of passive elements such as inductors and hence can have a profound impact in the field of RF integrated circuits

Abstract-Lattice-induced modulators at terahertz frequencies

Guillermo A. Naranjo and Xomalin G. Peralta

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-23-4780

We measured the transmission spectra of an array of split-ring resonators (SRRs) up to 10 terahertz for parallel and perpendicular polarizations. Calculations of the lattice and plasmon mode dispersion relations, in combination with electromagnetic simulations, confirm the presence of multiple higher-order lattice and plasmon modes. We modify the quality factor of higher-order plasmon resonances by modulating the lattice-plasmon mode coupling via changes in the period of the array. We also propose single frequency switches and a broadband dual-state amplitude modulator based on structured illumination that actively modifies the period of the SRR array.

© 2017 Optical Society of America

Abstract-Broadband absorber with periodically sinusoidally-patterned graphene layer in terahertz range

Longfang Ye, Yao Chen, Guoxiong Cai, Na Liu, Jinfeng Zhu, Zhengyong Song, and Qing Huo Liu

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-10-11223

We demonstrate that a broadband terahertz absorber with near-unity absorption can be realized using a net-shaped periodically sinusoidally-patterned graphene sheet, placed on a dielectric spacer supported on a metallic reflecting plate. Because of the gradient width modulation of the unit graphene sheet, continuous plasmon resonances can be excited, and therefore broadband terahertz absorption can be achieved. The results show that the absorber’s normalized bandwidth of 90% terahertz absorbance is over 65% under normal incidence for both TE and TM polarizations when the graphene chemical potential is set as 0.7 eV. And the broadband absorption is insensitive to the incident angles and the polarizations. The peak absorbance remains more than 70% over a wide range of the incident angles up to 60° for both polarizations. Furthermore, this absorber also has the advantage of flexible tunability via electrostatic doping of graphene sheet, which peak absorbance can be continuously tuned from 14% to 100% by controlling the chemical potential from 0 eV to 0.8 eV. The design scheme is scalable to develop various graphene-based tunable broadband absorbers at other terahertz, infrared, and visible frequencies, which may have promising applications in sensing, detecting, and optoelectronic devices.

© 2017 Optical Society of America

Abstract-Tunable Localized Surface Plasmon Resonances in a New Graphene-Like Si2BN’s Nanostructures

• Shi-Jia Yuan, 
• Hong Zhang, 
Xin-Lu Cheng

https://link.springer.com/article/10.1007/s11468-017-0592-3

The optical response of a new graphene-like material Si2BN’s nanostructures and some kinds of hybrid structures formed by Si2BN and metal nanoparticles was studied by using time-dependent density functional theory (TDDFT). We found that the periodic structures of Si2BN have wider absorption ranges than graphene. When the impulse excitation polarizes in different directions (armchair-edge direction and zigzag-edge direction), the absorption spectra of Si2BN nanostructures would be different (optical anisotropy). And in the hybrid structures, the increase of metal nanoparticles’ number brings the absorption intensity strengthening and red shift, which means a stronger ability of localized surface plasmon tuning. Also, the different metal nanoparticles were used to form the hybrid structures; they show an obviously different property as well. In addition, in the kinds of situations mentioned above, the plasmons were produced in visible region. This investigation provides an improved understanding of the plasmon enhancement effect in graphene-like photoelectric devices.

Abstract-High-order localized spoof surface plasmon resonances and experimental verifications

• Zhen Liao,
• Yu Luo,
• Antonio I. Fernández-Domínguez,
• Xiaopeng Shen,
• Stefan A. Maier
• & Tie Jun Cui

http://www.nature.com/srep/2015/150410/srep09590/full/srep09590.html

We theoretically demonstrated and experimentally verified high-order radial spoof localized surface plasmon resonances supported by textured metal particles. Through an effective medium theory and exact numerical simulations, we show the emergence of these geometrically-originated electromagnetic modes at microwave frequencies. The occurrence of high-order radial spoof plasmon resonances is experimentally verified in ultrathin disks. Their spectral and near-field properties are characterized experimentally, showing an excellent agreement with theoretical predictions. Our findings shed light into the nature of spoof localized surface plasmons, and open the way to the design of broadband plasmonic devices able to operate at very different frequency regimes.