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Qika Jia

Bio: Qika Jia is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Terahertz radiation & Laser. The author has an hindex of 11, co-authored 85 publications receiving 322 citations.


Papers
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Journal ArticleDOI
01 Aug 2004
TL;DR: The Shanghai deep ultraviolet free-electron laser source (SDUV-FEL) is an HGHG FEL facility designed for generating coherent output with wavelength down to 88 nm as mentioned in this paper.
Abstract: The Shanghai deep ultraviolet free-electron laser source (SDUV-FEL) is an HGHG FEL facility designed for generating coherent output with wavelength down to 88 nm. The design and the relevant R&D of this HGHG FEL source have been under way since 2000. Currently, a 150 MeV S-band electron injector is under construction as the first linac section to produce a high brightness beam. The design study and the present R&D status of the SDUV-FEL have been presented in this paper. (C) 2004 Elsevier B.V. All rights reserved.

32 citations

Journal ArticleDOI
TL;DR: In this article, a multi-color and multi-directional radiation by using sheet electron-beams to drive two-dimensional (2D) sub-wavelength hole arrays (SHAs) is investigated.
Abstract: We proposed and investigated, by theoretical analyses and simulations, a multi-color and multi-directional radiation by using sheet electron-beams to drive two-dimensional (2D) sub-wavelength hole arrays (SHAs). Each sub-wavelength hole is a resonant and radiative unit, which is successively excited by the electron-beam, such that the 2D SHA becomes a 2D array of radiating units and generates coherent Smith-Purcell radiation in specific directions where the radiation from all the units constructively interferes. The multi-color radiation is obtained when several resonant modes are excited. Each resonant mode could simultaneously radiate at several directions due to the multiple periodicity of the 2D SHA, and the radiation could be steered to any directions in the three dimensional space by adjusting the arrangement of 2D SHA and the electron energy. This radiation could promisingly be developed as radiation sources and devices with broad applications.

24 citations

Journal ArticleDOI
TL;DR: FELiChEM is a new experimental facility under construction at the University of Science and Technology of China (USTC), whose core device is two free electron laser oscillators generating middle infrared and far-infrared laser and covering the spectral range of 2.5-200 μm.
Abstract: FELiChEM is a new experimental facility under construction at the University of Science and Technology of China (USTC). Its core device is two free electron laser oscillators generating middle-infrared and far-infrared laser and covering the spectral range of 2.5–200 μm. It will be a dedicated infrared light source aiming at energy chemistry research. We present the brief design of the FEL oscillators, with the emphasis put on the middle-infrared oscillator. Most of the basic parameters are determined and the anticipated performance of the output radiation is given. The first light of FELiChEM is targeted for the end of 2017.

23 citations

Journal ArticleDOI
TL;DR: A terahertz Orotron based on the recently revealed special Smith-Purcell radiation was proposed and investigated in this paper, which can achieve high starting current density and low radiation power.
Abstract: We proposed and investigated a terahertz Orotron, which is based on the recently revealed special Smith–Purcell radiation. It overcomes the main obstacles of the traditional Orotron in the terahertz region—unreachable high starting-current-density and low radiation power. With the experimentally available electron beam and facilities, its average output power can reach hundreds of milliwatts and even several watts in terahertz region, which is many orders of magnitude higher than that of the traditional Orotron. Additionally, it can be controlled to operate in ether the first or the second order mode, and the radiation frequency can extend from 0.1 THz to 1 THz. These remarkable advantages make it a promising terahertz source for practical applications.

23 citations

Journal ArticleDOI
TL;DR: The recently uncovered special Smith-Purcell radiation (S-SPR) from the rectangular grating has significantly higher intensity than the ordinary SPR and its monochromaticity and directivity are also much better as discussed by the authors.
Abstract: The recently uncovered special Smith-Purcell radiation (S-SPR) from the rectangular grating has significantly higher intensity than the ordinary Smith-Purcell radiation (SPR). Its monochromaticity and directivity are also much better. Here we explored the mechanism of the S-SPR by applying the fundamental electromagnetic theory and simulations. We have confirmed that the S-SPR is exactly from the radiating eigen modes of the grating. Its frequency and direction are well correlated with the beam velocity and structure parameters, which indicates its promising applications in tunable wave generation and beam diagnostic.

23 citations


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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

01 Jan 2017
TL;DR: The 2017 roadmap of terahertz frequency electromagnetic radiation (100 GHz-30 THz) as mentioned in this paper provides a snapshot of the present state of THz science and technology in 2017, and provides an opinion on the challenges and opportunities that the future holds.
Abstract: Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz–30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.

690 citations

Journal ArticleDOI
TL;DR: In this paper, the ultrafast relaxation and recombination dynamics of photogenerated electrons and holes in epitaxial graphene were studied using optical-pump Terahertz-probe spectroscopy.
Abstract: The ultrafast relaxation and recombination dynamics of photogenerated electrons and holes in epitaxial graphene are studied using optical-pump Terahertz-probe spectroscopy. The conductivity in graphene at Terahertz frequencies depends on the carrier concentration as well as the carrier distribution in energy. Time-resolved studies of the conductivity can therefore be used to probe the dynamics associated with carrier intraband relaxation and interband recombination. We report the electron-hole recombination times in epitaxial graphene for the first time. Our results show that carrier cooling occurs on sub-picosecond time scales and that interband recombination times are carrier density dependent.

508 citations

Journal ArticleDOI
01 Sep 1967-Nature
TL;DR: High Energy Physics Vol 1 Edited by E H S Burhop (Pure and Applied Physics; a Series of Monographs and Textbooks Vol 25) Pp xi + 499 (New York: Academic Press, Inc; London: Academic Publications, Inc (London, Ltd, 1967) 176s as mentioned in this paper.
Abstract: High Energy Physics Vol 1 Edited by E H S Burhop (Pure and Applied Physics; a Series of Monographs and Textbooks Vol 25) Pp xi + 499 (New York: Academic Press, Inc; London: Academic Press, Inc (London), Ltd, 1967) 176s

257 citations

Journal Article
TL;DR: In this paper, a two-week loan copy of the paper is provided for the UCRL library at the University of California, Berkeley, which may be borrowed for two weeks.
Abstract: UCRL UNIVERSITY OF CALIFORNIA TWO-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Division, Ext. BERKELEY, CALIFORNIA

184 citations