PREFACE
With the rapid development of THz science and technology and its applications in various fields, numerous institutions and scientists from many countries have been paying great attention to the related research recently. Tens of thousands of researchers from different countries have been engaged in the relevant investigations. Furthermore, there are many THz connected academic conferences and seminars each year which attract thousands of scholars to participate. However, it is a great pity that so far there is no academic journal specifically devoted to the THz science and technology. Therefore, it is strongly suggested by THz experts that an international journal of Terahertz Science and Technology (TST) should be founded. And here it comes!
Aiming at all the scientists around the world, the International Organizing Committee (IOC) and all invited speakers of Shengzhen International Conference on Advanced Science and Technology (SICAST£¬the first conference held in Nov. 2007) agreed to affirm that TST will serve as a unique platform for all the papers presented in this influential biyearly international conference, and the IOC serves as the International Advisory Committee of the TST. Additionally, based on the successful website ¡°THz Research and Development Network¡± (http://www.thznetwork.org.cn), TST will also function as an open window to demonstrate the insightful tidings and the latest progressing of this field.
We sincerely believe that this journal, firstly initiated by the fourteen papers presented at SICAST2007, will be the ideal place for THz-related-idea exchanging and developing.
May all our efforts contribute to the advancing and progressing of THz science and technology!
Thank you.
Editorial Committee of TST
March., 2008
TST, Vol. 1, No. 1, PP. 1-8
Using Terahertz Spectroscopy to Study Nanomaterials
Charles A. Schmuttenmaer
Abstract: The microscopic details of carrier transport in nanocrystalline colloidal thin films is required for complete understanding of a variety of photochemical and photoelectrochemical cells utilizing interpenetrating networks. Measuring the photoconductivity and charge transport properties in these materials, however, is a challenging problem because of the inherent difficulty of attaching wires to nanometer-sized objects. Furthermore, picosecond (ps) carrier dynamics play an important role in efficient charge separation and transport, but the low temporal resolution of traditional methods used to determine the photoconductivity precludes their use in studying sub-ps to ps dynamics. Time-resolved THz spectroscopy (TRTS), on the other hand, is a non-contact electrical probe capable of measuring the photoconductivity on a sub-ps to nanosecond (ns) timescale. In this talk, TRTS is employed to determine the transient photoconductivity of ZnO nanowires, polycrystalline, and nanoparticle films, as well as dye-sensitized nanocrystalline colloidal TiO2 films. Electron injection occurs on sub-ps time scales. Decay kinetics (on hundreds of ps to ns time scales) indicate that surfaces and interfaces are the dominant sources of recombination. The photoconductivity deviates strongly from Drude behavior and is explained by disorder-induced carrier localization and/or backscattering of the photogenerated carriers. Trends as a function of material and morphology will be discussed.
Keywords: Terahertz Spectroscopy, Nanomaterials, Photoconductivity, Charge transport properties
doi: 10.11906/TST.001-008.2008.03.01
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TST, Vol. 1, No. 1, PP. 9-21
THz-Radiation ¨C a Probe in Solid State Physics
Michael von Ortenberg
Abstract (shortened version of talk at SICAST 2007): THz-radiation is the natural energy probe to investigate physical mechanisms in solids, because the corresponding transition energies are typically centered around 10 meV. To distinguish, however, in solids between ionic and electronic transitions an external magnetic field as ¡°filter¡± has to be applied. Whereas the magnetic field tunes the electronic energies, the ionic levels are not affected. A review of THz-magneto spectroscopy covering a total of three decades in energy around 1 THz in magnetic fields up to 1,000 Tesla is given.
Keywords: Magnetospectroscopy, FIR/THz, Semiconductor, Megagauss
doi: 10.11906/TST.009-021.2008.03.02
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TST, Vol. 1, No. 1, PP. 22-27
Terahertz frequency quantum cascade lasers: growth and measurement
S. P. Khanna, S. Chakraborty, M. Lachab,N. M. Hinchcliffe, P. Dean, E. H. Linfield, and A. G. Davies
Abstract: Results are presented for two GaAs-AlGaAs quantum cascade laser (QCL) structures that emit at frequencies of 2.59 THz and 2.75 THz. Both structures have a nominally identical, bound-to-continuum active region design, and the difference between their emission frequencies is interpreted as resulting from small differences in the gallium and aluminium growth rates, which were measured both before and after laser growth using a pyrometric spectrometry technique. The same technique allows the QCL growth to be monitored real-time, and drifts in growth rates identified.
Keywords: Terahertz£¬Quantum cascade lasers
doi: 10.11906/TST.022-027.2008.03.03
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TST, Vol. 1, No. 1, PP. 28-36
Laser Terahertz Emission Microscope
M. Tonouchi, N. Uchida, S. Kim, R. Inoue, and H. Murakami
Abstract: Laser terahertz (THz) emission microscope (LTEM) is reviewed. Femtosecond lasers can excite the THz waves in various electronic materials due to ultrafast current modulation. The current modulation is realized by acceleration or deceleration of photo-excited carriers, and thus LTEM visualizes dynamic photo-response of substances. We construct free-space type and scanning probe one with transmission or reflection modes. The developed systems have a minimum spatial resolution better than 2 ¦Ìm, which is defined by the laser beam diameter. We also present some examples of LTEM applications.
Keywords: Terahertz radiation, Microscope, High resolution active imaging
doi: 10.11906/TST.028-036.2008.03.04
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TST, Vol. 1, No. 1, PP. 37-41
Properties of Terahertz Superconducting Hot Electron Bolometer Mixers
J. Chen L. Kang B. B. Jin W. W. Xu P.H. Wu W. Zhang L. Jiang N. Li S.C. Shi and G.N. Gol¡¯tsman
Abstract: A quasi-optical superconducting niobium nitride (NbN) hot electron bolometer (HEB) mixer has been fabricated and measured in the terahertz (THz) frequency range of 0.5~2.52 THz. A receiver noise temperature of 2000 K at 2.52 THz has been obtained for the mixer without corrections. Also, the effect of a Parylene C anti-reflection (AR) coating on the silicon (Si) lens has been studied.
Keywords: Hot electron bolometer (HEB) mixer, Terahertz, Noise temperature, Heterodyne detector
doi: 10.11906/TST.037-041.2008.03.05
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TST, Vol. 1, No. 1, PP. 42-50
Electromagnetic Metamaterials for Terahertz Applications
Hou-Tong Chen, Willie J. Padilla, Richard D. Averitt, Arthur C. Gossard, Clark Highstrete, Mark Lee, John F. O¡¯Hara, and Antoinette J. Taylor
Abstract: The recently developed class of artificially structured composite materials, termed metamaterials, has shown increasing importance in accomplishing necessary functional devices for THz applications. We have created a series of novel planar electric metamaterials operating at THz frequencies. Alteration of substrate properties has resulted in actively and dynamically switchable THz metamaterial devices. High efficiency, all-electronic THz switching and modulation operating at room temperature have been accomplished by the use of a hybrid of metamaterial and Schottky diode structure. Dynamic switching of THz radiation was also achieved by photoexcitation of the semiconductor substrate, where ultrafast switching has been demonstrated by the use of an ErAs/GaAs nanoisland superlattice substrate.
Keywords: Metamaterials, Terahertz
doi: 10.11906/TST.042-050.2008.03.06
