Abstract-Characterization of a graphene-based terahertz hot-electron bolometer

H. Gao, W. Miao, Z. Wang, W. Zhang, Y. Geng, S. C. Shi, C. Yu, Z. Z. He, Q. B. Liu, Z. H, Feng

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10826/108260X/Characterization-of-a-graphene-based-terahertz-hot-electron-bolometer/10.1117/12.2500700.short?SSO=1

Graphene has an extremely weak coupling of electrons to phonons due to its nonionic character of lattice. This remarkable property makes graphene very attractive for hot electron bolometers (HEBs). In this paper, we present the development of a graphene-based terahertz hot electron bolometer (HEB) with Johnson noise readout. The HEB is essentially a graphene microbridge that is connected to a log spiral antenna by Au contact pads. We study the responsivity, noise equivalent power (NEP) and time constant of the graphene-based HEB in a perpendicular magnetic field. In order to understand the thermal transport inside the graphene microbridge, we also measure the graphene-based HEB at different bath temperatures between 3 K and 10 K. Detailed experimental results and analysis will be presented.

© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Abstract-Broadband Terahertz Generation via the Interface Inverse Rashba-Edelstein Effect

C. Zhou, Y. P. Liu, Z. Wang, S. J. Ma, M. W. Jia, R. Q. Wu, L. Zhou, W. Zhang, M. K. Liu, Y. Z. Wu, and J. Qi

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.086801

Novel mechanisms for electromagnetic wave emission in the terahertz frequency regime emerging at the nanometer scale have recently attracted intense attention for the purpose of searching next-generation broadband THz emitters. Here, we report broadband THz emission, utilizing the interface inverse Rashba-Edelstein effect. By engineering the symmetry of the $\mathrm{Ag}/\mathrm{Bi}$ Rashba interface, we demonstrate a controllable THz radiation ($\sim 0.1–5\mathrm{THz}$) waveform emitted from metallic $\mathrm{Fe}/\mathrm{Ag}/\mathrm{Bi}$heterostructures following photoexcitation. We further reveal that this type of THz radiation can be selectively superimposed on the emission discovered recently due to the inverse spin Hall effect, yielding a unique film thickness dependent emission pattern. Our results thus offer new opportunities for versatile broadband THz radiation using the interface quantum effects.

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Abstract-Broadband terahertz generation via the interface inverse Rashba-Edelstein effect

C. Zhou, Y. P. Liu, Z. Wang, S. J. Ma, M. W. Jia, R. Q. Wu, L. Zhou, W. Zhang, M. K. Liu, Y. Z. Wu, and J. Qi, 

https://journals.aps.org/prl/accepted/7f07dY95Df118160072f78c38ad2d3d9134dfaf91

Novel mechanisms for electromagnetic wave emission in the terahertz (THz) frequency regime emerging at the nanometer scale have recently attracted intense attention for the purpose of searching next-generation broadband THz emitters. Here, we report broadband THz emission, utilizing the interface inverse Rashba-Edelstein effect. By engineering the symmetry of the Ag/Bi Rashba interface, we demonstrate a controllable THz radiation (\textasciitilde 0.1-5 THz) waveform emitted from metallic Fe/Ag/Bi heterostructures following photo-excitation. We further reveal that this type of THz radiation can be selectively superimposed on the emission discovered recently due to the inverse Spin Hall effect, yielding a unique film thickness dependent emission pattern. Our results thus offer new opportunities for versatile broadband THz radiation using the interface quantum effects. Terahertz (THz) radiation from 0.1--30 THz accesses a diverse group of low-energy elementary excitations in solid-state systems [1], holding great promises for imaging, sensing and security applications [2]. One major challenge in the next generation THz technology is to search novel mechanism(s) providing efficient and broadband THz radiation with a gapless spectrum [3-5]. To date, most broadband THz emission devices [2-5] are based on the femtosecond laser excitations, taking advantage exclusively of the nonlinear or dynamic properties of the electrons. Recently, the emerging ultrafast spintronics [6-13], however, offers an alternative route to the THz emission with the spin-degree of freedom, by converting spin current bursts into THz pulses. In this way, one can effectively generate, control, and detect the spin currents, as well as utilize such spin-to-charge conversion [6-13] within the sub-picosecond timescale to yield efficient ultra-broadband THz emission. Such ultrafast spin-to-charge conversion process in all previous works is mostly based on the inverse Spin Hall effect (ISHE) (14-15), which happens inside the bulk of a metallic system with a strong spin-orbit coupling (SOC). In contrast, the inverse Rashba-Edelstein effect (IREE) occurring at the interfaces with broken inversion symmetry can also provide efficient spin-to-charge conversion [16-19]. In the IREE, the generated charge current in two-dimensional electron gas can be described by [19]$$j_c\propto {\lambda }_{IREE}{j}_s\times \hat{z}$$where ${\lambda }_{IREE}$ is the IREE coefficient which is proportional to the Rashba parameter ${\alpha }_R$, $\hat{z}$ is the direction of the potential gradient (interfacial electric field) perpendicular to the interface, and $j_s$ is the spin current. Although the IREE has been intensively studied under equilibrium or quasi-equilibrium conditions in magnetoresistance measurements [17], non-local spin valves [18], and ferromagnetic resonance experiments [19], it is still elusive whether the IREE can work in femtosecond timescale, and play a vital role in the THz emission. In this work, we report the observation of THz radiation via the interface IREE in the metallic Fe/Ag/Bi heterostructures, which strongly suggests the effect of the interface IREE on the spin-to-charge conversion in femtosecond timescale. This observation brings us to a novel mechanism of emitting ...

Abstract-Broadband terahertz generation via the interface inverse Rashba-Edelstein effect

C. Zhou, Y. P. Liu, Z. Wang, S. J. Ma, M. W. Jia, R.Q. Wu, L. Zhou, W. Zhang, M. K. Liu, Y. Z. Wu, J. Qi

https://128.84.21.199/abs/1804.04765v1

Novel mechanisms for electromagnetic wave emission in the terahertz (THz) frequency regime emerging at the nanometer scale have recently attracted intense attention for the purpose of searching next-generation broadband THz emitters. Here, we report a new mechanism for broadband THz emission, utilizing the interface inverse Rashba-Edelstein effect. By engineering the symmetry of the Ag/Bi Rashba interface, we demonstrate a controllable THz radiation (~0.1-5 THz) waveform emitted from metallic Fe/Ag/Bi heterostructures following photo-excitation. We further reveal that this type of THz radiation can be selectively superimposed on the emission discovered recently due to the inverse Spin Hall effect, yielding a unique film thickness dependent emission pattern. Our results thus offer new opportunities for versatile broadband THz radiation using the interface quantum effects.

Abstract-THz artificial dielectric isolator

R. Mendis,  M. Nagai,   W. Zhang,   D. M. Mittleman

http://ieeexplore.ieee.org/document/8066918/

We experimentally demonstrate an isolator suitable for the THz spectral regime. The isolator is designed by combining a polarizing beamsplitter with a quarter-wave plate, both based on the same artificial-dielectric technology. The artificial-dielectric medium comprises of a stack of 30 μm thick metal plates that form an array of parallel-plate waveguides. The isolator exhibits an isolation of 52 dB with an insertion loss less than one dB, at a frequency of 0.46 THz, which rivals the performance of commercially available Faraday isolators for optical wavelengths.

Abstract-III-nitride terahertz photodetectors for the Reststrahlen gap of intersubband optoelectronics

R. Paiella,  H. Durmaz,  F. F. Sudradjat; D. Nothern, G. C. Brummer, W. Zhang; J. Woodward,  T. D. Moustakas

https://www.spiedigitallibrary.org/proceedings/Download?fullDOI=10.1117/12.2274040

We report the development of terahertz intersubband photodetectors based on GaN/AlGaN quantum wells, covering the frequency range that is fundamentally inaccessible to existing III-V semiconductor devices due to Reststrahlen absorption. Two different approaches have been employed to mitigate the deleterious effects of the intrinsic polarization fields of nitride heterostructures: the use of suitably designed double-step quantum wells, and epitaxial growth on semipolar GaN substrates. Promising results are obtained with both approaches, which could be extended to other device applications as a way to utilize the intrinsic advantages of nitride semiconductors for THz intersubband optoelectronics.
© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Abstract-Broadband Terahertz Transparency in a Switchable Metasurface

Su, X.
Ouyang, C. ; Xu, N. ; Tan, S. ; Gu, J. ; Tian, Z. ; Han, J. ; Yan, F. ; Zhang, W.

http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?reload=true&arnumber=7008493

Plasmon-induced transparency in terahertz metamaterials markedly modifies the dispersive properties of an otherwise opaque medium and reveals unprecedented prospects on novel functional components. However, plasmon-induced transparency in metamaterials so far exists in a narrow frequency band or without actively tunable abilities. Here, we demonstrate optical control of a broadband plasmon-induced transparency in a hybrid metamaterial made from integrated silicon–metal unit cells. Attributed to the modification in damping rate of the dark mode resonators under optical excitation, a giant dynamic amplitude modulation of the broadband transparency window is observed. The scheme suggested here is promising in developing broadband active slow-light devices and realizing on-to-off switching responses of the terahertz radiation at room temperature.

(a) Schematic diagram of the active broadband PIT metamaterial. The geometrical parameters are: $l = 86 muhbox{m}$, $a = 28 muhbox{m}$, $b = 48 muhbox{m}$, $w = 4 muhbox{m}$, $D_{rm x}= 26 muhbox{m}$, $D_{rm y}= 10 muhbox{m}$, $P_{rm x}= 114 muhbox{m}$, and $P_{rm y}= 134 muhbox{m} $. The bottom right of panel (a) is a microscopic image of the fabricated metamaterial. (b) Experimental diagram of the optical pump-terahertz probe measurement.

Published in:

Photonics Journal, IEEE  (Volume:7 ,  Issue: 1 )

Article#:

5900108

ISSN :

1943-0655

DOI:

10.1109/JPHOT.2015.2390146

Date of Publication :

13 January 2015

Date of Current Version :

30 January 2015

Issue Date :

Feb. 2015

Sponsored by :

IEEE Photonics Society

Publisher:

IEEE

Abstract-A pseudo-planar metasurface for a polarization rotator

http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-22-9-10446&id=284135

W. Zhang, W. M. Zhu, E. E. M. Chia, Z. X. Shen, H. Cai, Y. D. Gu, W. Ser, and A. Q. Liu  »View Author Affiliations

Optics Express, Vol. 22, Issue 9, pp. 10446-10454 (2014)
http://dx.doi.org/10.1364/OE.22.010446

New demonstrations of effective interaction between light and artificially electromagnetic interface, or the metasurface, have stimulated intensive research interests on control of light to realize applications in beam steering, optical imaging and light focusing, etc. Here we reported a new type of planar metasurface of which every individual metamolecule is single metallic layer with stereo structure and the metasurface is name as Pseudo-Planar Metasurface (PPM). The metamolecule of the PPM is a chiral structure and therefore derives significant optical activity.

© 2014 Optical Society of America