International Journal of Terahertz Science and Technology
Vol.5, No.1, March 2012. PP.1-66 (5)
date:2012-03-31 15:52:30 Click No.:4264

TST, Vol. 5, No. 1, PP. 1-10

(Invited Paper) THz Electron Spin Resonance on Nanomagnets

Hiroyuki Nojiri 1*, 2, Z. W. Ouyang 2
1
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
2 Wuhan National High Magnetic Field Center, HUST, Wuhan, 430074, China.
* 1 E-mail:
nojiri@imr.tohoku.ac.jp

(Received February 18, 2012)

Abstract: Recent results of THz Electron Spin Resonance (ESR) on nanomagnets were reviewed. This article addresses (1) investigation of exchange coupling in heterometallic nanomagnets and chemical trends, (2) spin freezing in a giant nanomagnet, where quasi-spin wave like excitation is found without a phase transition in thermodynamic limit, and (3) pulsed EPR on a spin coherent experiment. Recent development of a tabletop THz spectrometer using a mini-pulsed magnet is also described. The development of a high-frequency ESR station at the Wuhan National High Magnetic Field Center at HUST is also introduced briefly. This article demonstrates the power of THz ESR for investigations of nanomagnets.

Keywords: Terahertz electron spin resonance, Nanomagnet, High magnetic field

doi: 10.11906/TST.001-010.2012.03.01

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TST, Vol. 5, No. 1, PP. 11-17

(Invited Paper) Towards Future THz Communications Systems

Thomas Kürner *
Technische Universität Braunschweig, Institut für Nachrichtentechnik, Terahertz Communications Lab, Schleinitzstr. 22, D-38092 Braunschweig, Germany
* Email:
t.kuerner@tu-bs.de

(Received February 14, 2012)

Abstract: Carrier frequencies beyond 300 GHz, belonging to the so-called THz range, have received attention for considering this frequency band for future multi-gigabit short-range communication systems. This review paper gives an overview of current issues in the emerging field of THz communications targeting to deliver wireless 100 Gbps over short distances. The paper will start by introducing scenarios and applications requiring such high data rates followed by a discussion on the radio channel characteristics. In the 300 GHz frequency band, the path loss is even more significant than at 60 GHz and appropriate measures to mitigate effects in none-line-of-sight (NLOS) cases, caused e. g. by the influence of moving people, are required. Advanced antenna techniques like beam forming or beam switching are a pre-requisite to guarantee seamless service. In order to consider such techniques in the standards development, the propagation channel operating at these mm- and sub-mm wave bands in realistic environments must be well understood. Therefore, intensive channel measurement and modeling activities have been done at 300 GHz, which started a couple of years ago at Terahertz Communications Lab (TCL). Due to the short wave length, the influence of surface roughness of typical building materials plays an important role. Hence, the modeling of rough surface scattering has been one of the main areas in these investigations. In this contribution, the main results of the propagation research activities at TCL are summarized. In the last part of the paper, an overview of the state-of-the-art in technology development and successful demonstrations of data transmission will be given together with a report on the status quo of ongoing activities in standardization at IEEE 802.15 IG THz and the regulation of the spectrum beyond 300 GHz.

Keywords: THz Communications, Multi-gigabit wireless data rates, Channel characterization, Regulation and standardization

doi: 10.11906/TST.011-017.2012.03.02

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TST, Vol. 5, No. 1, PP. 18-39

(Invited Paper) Generation of High Power THz Waves in Relativistic Electron Beam Plasma and Two-Sheet-Beam FEM

M.K.A. Thumm 1*, 5*, A. V. Arzhannikov 1, 2, V.T. Astrelin 1, 2, A.V. Burdakov 1-3, N.S. Ginzburg 4, I.A. Ivanov 1, 2, P.V. Kalinin 1, 2, S. A. Kuznetsov 1, 2, M.A. Makarov 2, K. I. Mekler 2, A.G. Paulish 1, N. Yu. Peskov 4, S. V. Polosatkin 1, 2, S.A. Popov 2, V. V. Postupaev 1, 2, A. F. Rovenskikh 2, A.S. Sergeev 4, S. L. Sinitsky 1, 2, V. F. Sklyarov 2, 3, V.D. Stepanov 1, 2, L. N. Vyacheslavov 1, 2, V. Yu. Zaslavsky 4
1
Novosibirsk State University (NSU), Novosibirsk, Russia
 * 1 Email:
thumm@nsm.nsu.ru
2 Budker Institute of Nuclear Physics (BINP) SB RAS, Novosibirsk, Russia
3 Novosibirsk State Technical University (NSTU), Novosibirsk, Russia
4 Institute of Applied Physics (IAP) RAS, Nizhny Novgorod, Russia
5 Karlsruhe Institute of Technology (KIT), IHM, Karlsruhe, Germany
 * 5 Email:
manfred.thumm@kit.edu

(Received December 23, 2011)

Abstract: Sub-mm wave and THz radiation can be generated by the process of transformation of plasma waves into electromagnetic (EM) radiation at strong Langmuir (LT) turbulence via a two-stream instability induced by a propagating high current relativistic electron beam (REB). Plasmon scattering on plasma density fluctuations yields EM emission at the plasma frequency wp (“wp‑process”). Nonlinear plasmon-plasmon merging results in the generation of photons nearby the 2nd harmonic of the plasma frequency 2wp (“2wp‑process”). For plasma densities 1014-1015 cm-3, corresponding radiation frequencies are located in the range of sub-mm waves: 180-566 GHz. The power density of LT-induced sub-mm-wave emission from plasmas in the multi-mirror trap GOL-3 (BINP) during injection of a 10-ms-REB at plasma densities ne » 5∙1014 cm-3 , electron temperatures Te » 1.5 keV and magnetic field B » 4 T was measured to be up to 5-10 kW/cm3 in the frequency band above 100 GHz.

Former experiments on the ELMI device (BINP) demonstrated the operation of an mm-wave single channel free electron maser (FEM) with planar cavity geometry and 2D distributed feedback. Measurements have shown single mode single-frequency generation (75 GHz) with about 300 ns pulse duration at the power level of 20-40 MW. In the case of two parallel sheet electron beams in two slit channels, we plan to investigate an inter-cavity scattering scheme for two-stage generation of sub-mm wave radiation. As a first step we have studied simultaneous generation and transport of two intense sheet electron beams in two FEM slit channels. The REB parameters were the following: electron energy 0.8 MeV, total current of each beam 3 kA, cross section 0.4 cm x 7 cm and pulse duration 3 ms. The measurements of the energy of the mm-wave radiation pulse for frequencies higher than 70 GHz gave a value of  4-6 J and the average power of 20-40 MW from each of the two FEM channels.

Both the GOL-3 and FEM experiments need components and systems for spectral diagnostics of sub-mm wave radiation. Novel micro-structured quasi-optical elements have been developed where amplitude, phase and polarization responses are controlled by frequency selective surface (FSS) topologies, manufactured by photolithography and electroforming. Bandpass filters (70 mm aperture diameter) with center frequency (CF) from 112 to 376 GHz show > 90% transmission and have a FWHM bandwidth of ~ 12%. Meta-material absorbers for real-time THz imaging (CF from 310 to 370 GHz) have an absorption of > 90% and excellent thermal insulation.

Keywords: Terahertz generation and spectroscopy, Electron beam plasma, Free electron maser, Frequency selective surfaces

doi: 10.11906/TST.018-039.2012.03.03

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TST, Vol. 5, No. 1, PP. 40-47

(Invited Paper) Sub-THz quasi-optical wave control components

Michael Petelin *
Institute of Applied Physics, Nizhny Novgorod, Russian Academy of Sciences
* E-mail:
petelin@appl.sci-nnov.ru

(Received January 22, 2012)

Abstract: In applications to the plasma fusion, material diagnostics, particle acceleration, radar and communication, at frequencies approaching the THz region, the standard microwave transmission and control components need to be replaced with their oversized, quasi-optical, analogs.

Keywords: Quasi-optical waveguides and cavities, Mode converters, Filters, Multiplexers and duplexers.

doi: 10.11906/TST.040-047.2012.03.04

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TST, Vol. 5, No. 1, PP. 48-66

(Invited Paper) THz Photonics: The Synergy of Ultrafast Optics, Electronics, Micro-Microwaves and Quasi-Optics

Daniel R. Grischkowsky *
School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, OK 74078, USA
* Email:
daniel.grischkowsky@okstate.edu

(Received February 12, 2012)

Abstract: Ultrafast THz photonics has demonstrated the capability to create and to measure guided wave and freely propagating subps electrical pulses, which are much shorter than those produced and measured by any other method.  THz photonics will be reviewed, starting with the use of photo-conductive switching on lithographically fabricated transmission lines on semiconductor chips. Lithographically fabricated, micron-sized antennas, when photo-conductively driven by subps laser pulses, radiate well into the THz regime. Freely propagating THz-TDS and Waveguide THz-TDS measurements will be presented. Future opportunities in fundamental research and practical applications, including THz communications, will be described.

Keywords: THz-TDS, Quasi-Optics, Photoconductive Switching, and THz Communications

doi: 10.11906/TST.048-066.2012.03.05

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