scispace - formally typeset
Search or ask a question
Author

Norihiko Sekine

Bio: Norihiko Sekine is an academic researcher from National Institute of Information and Communications Technology. The author has contributed to research in topics: Terahertz radiation & Photomixing. The author has an hindex of 14, co-authored 160 publications receiving 877 citations.


Papers
More filters
Journal ArticleDOI
01 Oct 2007
TL;DR: The current status of developments in developments in terahertz quantum cascade lasers, quantum well photodetectors, and an example of a database for materials of fine art are reported, and results obtained from measuring atmospheric propagation are reported.
Abstract: The National Institute of Information and Communications Technology (NICT, Japan) started the Terahertz Project in April 2006. Its fundamental purpose in the next five years is to enable a nationwide technical infrastructure to be created for diverse applications of terahertz technology. The technical infrastructure includes the development of semiconductor devices such as terahertz quantum cascade lasers, terahertz-range quantum well photodetectors, and high-precision tunable continuous wave sources. It also includes pulsed terahertz measurement systems, modeling and measurement of atmospheric propagation, and the establishment of a framework to construct a materials database in the terahertz range including standardization of the measurement protocol. These are common technical infrastructure even in any terahertz systems. In this article, we report the current status of developments in these fields such as terahertz quantum cascade lasers (THz-QCLs) (with peak power of 30 mW, 3.1 THz), terahertz-range quantum well photodetectors (THz-QWPs) (tuned at 3 THz) an ultrawideband terahertz time domain spectroscopy (THz-TDS) system (with measurement range of from 0.1 to 15 THz), an example of a database for materials of fine art, and results obtained from measuring atmospheric propagation.

202 citations

Proceedings ArticleDOI
03 Apr 2008
TL;DR: In this paper, the authors made experiments on real-time imaging of THz radiation from Quantum Cascade Laser (QCL), using vanadium oxide (VOx) microbolometer in frared focal plane arrays (IRFPAs) of 320x240 with pitches of 37 µm and 23.5 µm.
Abstract: The authors made experiments on real-time imaging of THz radiation from Quantum Cascade Laser (QCL), using vanadium oxide (VOx) microbolometer in frared focal plane arrays (IRFPAs) of 320x240 with pitches of 37 µm and 23.5 µm as well as 640x480 with 23.5µm pitch. The QCL has such parameters as 3.1 THz emission frequency and time averaged power of a bout 10 µW at 15K operation temperature. Using QCL and current VOx IRFPAs, Noise Equivalent Power (NEP) was measured at 3.1 THz and found 200~300 pW. To improve NEP or THz signal, THz absorption layer was added to pixel structure of the current 320x240 IRFPA with 23.5µm pitch and THz transmissivity of package window was also increased. NEP values for improved FPAs were measured and NEP value of 40 pW was obtained at 3.1 THz. Finally, effect of pixel integration on NEP was investigated for frame integration of 64 frames and it is found that NEP value as low as 1 pW is achievable. Keywords : Terahertz, Real-time imaging, Microbolometer, Focal plane arrays, THz absorption layer 1. INTRODUCTION

72 citations

Journal ArticleDOI
TL;DR: In this article, the performance of a four-level scheme terahertz quantum cascade laser (4L-QCL) with the nonequilibrium Green's function method was analyzed.
Abstract: We have calculated the performance of a recently proposed four-level scheme terahertz quantum cascade laser (4L terahertz-QCL) with the nonequilibrium Green’s function method. The calculation result for 40 K showed that the 4L QCL has a larger terahertz gain than the conventional resonant phonon QCL. This is because a large number of electrons accumulate in the upper lasing level and contribute to lasing in the new scheme. When the temperature is increased, the advantage of gain decreases due to thermally activated phonon scattering.

59 citations

Proceedings ArticleDOI
04 Oct 2017
TL;DR: In this article, a 300-GHz CMOS receiver operating above NMOS/max was reported. But the receiver's conversion gain, noise figure, and 3-dB bandwidth were −19.5 dB, 27 dB, and 26.5 GHz, respectively.
Abstract: Building receivers (RXs) that operate above the transistor unity-power-gain frequency, f max , is extremely challenging because an LNA-less architecture must be adopted. This paper reports on a 300-GHz CMOS RX operating above NMOS /max. Its conversion gain, noise figure, and 3-dB bandwidth are, respectively, −19.5 dB, 27 dB, and 26.5 GHz. The RX achieved a wireless data rate of 32 Gb/s with 16QAM. It shows the potential of moderate-/f max CMOS technology to be used for ultrahigh-speed THz wireless communications.

41 citations

Proceedings ArticleDOI
TL;DR: In this paper, the authors developed two types of THz-FPAs, broad-band and narrow-band, and evaluated their performance on passive and active THz imaging experiments.
Abstract: Uncooled Terahertz (THz) focal plane array (FPA), 320x240 format-23.5 μm pitch, and THz imager were developed. There are two types of THz-FPAs, i.e., broad-band type and narrow-band type. Since broad-band type THz-FPA was developed, a couple of modifications have been made to improve Noise Equivalent Power. The narrow-band type THz-FPA has such a new structure that Si cover is put above thermal isolation structure of broad-band type THz-FPA at a distance of half of wavelength of interest. Measurements on responsivities of narrow-band type FPAs show enhancement by a factor of ca. 3. Lock-in imaging technique has been developed, which increases signal-to-noise ratio as a function of square root of the number of frames of integration. Both passive and active THz imaging experiments were finally described.

33 citations


Cited by
More filters
Journal ArticleDOI

[...]

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

Journal ArticleDOI
TL;DR: The 2017 roadmap of terahertz frequency electromagnetic radiation (100 GHz-30 THz) as discussed by the authors 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.

1,068 citations

Journal ArticleDOI
TL;DR: An overview of emerging technologies and system research that might lead to ubiquitous THz communication systems in the future is given.
Abstract: The increasing demand of unoccupied and unregulated bandwidth for wireless communication systems will inevitably lead to the extension of operation frequencies toward the lower THz frequency range. Higher carrier frequencies will allow for fast transmission of huge amounts of data as needed for new emerging applications. Despite the tremendous hurdles that have to be overcome with regard to sources and detectors, circuit and antenna technology and system architecture to realize ultrafast data transmission in a scenario with extensive transmission loss, a new area of research is beginning to form. In this article we give an overview of emerging technologies and system research that might lead to ubiquitous THz communication systems in the future.

878 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: This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979-2014.
Abstract: Visible Light Communication (VLC) is an emerging field in Optical Wireless Communication (OWC) which utilizes the superior modulation bandwidth of Light Emitting Diodes (LEDs) to transmit data. In modern day communication systems, the most popular frequency band is Radio Frequency (RF) mainly due to little interference and good coverage. However, the rapidly dwindling RF spectrum along with increasing wireless network traffic has substantiated the need for greater bandwidth and spectral relief. By combining illumination and communication, VLC provides ubiquitous communication while addressing the shortfalls and limitations of RF communication. This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979–2014. VLC is compared with infrared (IR) and RF systems and the necessity for using this beneficial technology in communication systems is justified. The advantages of LEDs compared to traditional lighting technologies are discussed and comparison is done between different types of LEDs currently available. Modulation schemes and dimming techniques for indoor VLC are discussed in detail. Methods needed to improve VLC system performance such as filtering, equalization, compensation, and beamforming are also presented. The recent progress made by various research groups in this field is discussed along with the possible applications of this technology. Finally, the limitations of VLC as well as the probable future directions are presented.

687 citations