Author
Nakajima Fumito
Other affiliations: Hitachi
Bio: Nakajima Fumito is an academic researcher from Nippon Telegraph and Telephone. The author has contributed to research in topics: Photodiode & Avalanche photodiode. The author has an hindex of 13, co-authored 65 publications receiving 1074 citations. Previous affiliations of Nakajima Fumito include Hitachi.
Topics: Photodiode, Avalanche photodiode, Signal, Exhaust gas, Laser linewidth
Papers published on a yearly basis
Papers
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TL;DR: In this article, a 120-GHz-band wireless link that uses millimeter-wave photonic techniques was developed, which achieved error-free transmission of OC-192 and 10-GbE signals over a distance of more than 200 m with a received power of below -30 dBm.
Abstract: A 120-GHz-band wireless link that uses millimeter-wave (MMW) photonic techniques was developed. The output power and noise characteristics of 120-GHz-band MMWs generated by converting a 125-GHz optical subcarrier signal were evaluated. It was then shown that the noise characteristics of the 125-GHz signal generated with these photonic technologies is sufficient for 10-Gb/s data transmission. We constructed a compact 120-GHz-band wireless link system, and evaluated its data transmission characteristics. This system achieved error-free transmission of OC-192 and 10-GbE signals over a distance of more than 200 m with a received power of below -30 dBm.
300 citations
TL;DR: In this article, an antenna-integrated uni-travelling-carrier photodiodes with a quasi-optical output port fabricated for practical use generates almost the same output power as the chip at around 1.04 THz with good linearity.
Abstract: Photonic generation of continuous millimetre- and sub-millimetre waves up to the THz range using antenna-integrated uni-travelling-carrier photodiodes is described. A device integrating a wideband log-periodic antenna exhibits a maximum output power of 2.6 ?W at 1.04 THz with good linearity. A module with a quasi-optical output port fabricated for practical use generates almost the same output power as the chip at around 1 THz and operates at frequencies of up to 1.5 THz. The output power level and the operation frequency are records for wideband photodiodes operating at 1.55 ?m. Devices integrating resonant narrowband dipole antennae have also been fabricated and the output power increases at resonant peak frequencies confirmed. The device having a peak at 1.04 THz exhibits a maximum (detected) output power of 10.9??W at 1.04 THz with good linearity. This output power is the highest value ever directly generated from a photodiode in the THz range, and several times higher than the maximum value reported by the low-temperature-grown GaAs photoconductive switch at around 1 THz.
163 citations
TL;DR: In this article, a uni-traveling-carrier photodiode (UTC-PD) is integrated with a wideband log-periodic toothed antenna for generating millimeter and sub-millimeter waves at frequencies of up to terahertz range.
Abstract: A uni-traveling-carrier photodiode (UTC-PD) is monolithically integrated with a wideband log-periodic toothed antenna for generating millimeter and submillimeter waves at frequencies of up to terahertz range. A module with a quasi-optical output port fabricated for practical use operates up to 1.5 THz and generates an output power of 2.3 /spl mu/W at 1.04 THz with good linearity. The output power level and the operation frequency are records for wideband PD modules operating at 1.55 /spl mu/m. An investigation of the operational characteristics of the UTC-PD reveals that the effective use of the electron-velocity overshoot in the junction depletion layer is important for maximizing the output power in the terahertz range.
148 citations
TL;DR: In this paper, an antenna-integrated uni-travelling-carrier photodiode is investigated for the generation of millimetre/sub-millimetre waves up to terahertz range using an antenna integrated UAV.
Abstract: Photonic generation of millimetre/sub-millimetre waves up to terahertz range using an antenna-integrated uni-travelling-carrier photodiode is investigated A test device measured on-wafer exhibits a record maximum output-power of 26 µW at 104 THz with good linearity A fabricated quasi-optical module operates at frequencies of up to 15 THz
80 citations
TL;DR: In this paper, the fabrication of uni-travelling-carrier photodiodes with a resonant antenna for generating high-power continuous terahertz waves is reported.
Abstract: The fabrication of uni-travelling-carrier photodiodes with a resonant antenna for generating high-power continuous terahertz waves is reported. Enhancement of the output power is achieved at frequencies from 0.7 to 1.6 THz, and the maximum output power obtained at 1.04 THz is 10.9 µW.
58 citations
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TL;DR: An overview of the status of the terahertz technology, its uses and its future prospects are presented in this article, with a focus on the use of the waveband in a wide range of applications.
Abstract: Research into terahertz technology is now receiving increasing attention around the world, and devices exploiting this waveband are set to become increasingly important in a very diverse range of applications. Here, an overview of the status of the technology, its uses and its future prospects are presented.
5,512 citations
TL;DR: The terahertz time-domain spectroscopy (THz-TDS) as discussed by the authors is a new spectroscopic technique based on coherent and time-resolved detection of the electric field of ultrashort radiation bursts.
Abstract: Over the past three decades a new spectroscopic technique with unique possibilities has emerged. Based on coherent and time-resolved detection of the electric field of ultrashort radiation bursts in the far-infrared, this technique has become known as terahertz time-domain spectroscopy (THz-TDS). In this review article the authors describe the technique in its various implementations for static and time-resolved spectroscopy, and illustrate the performance of the technique with recent examples from solid-state physics and physical chemistry as well as aqueous chemistry. Examples from other fields of research, where THz spectroscopic techniques have proven to be useful research tools, and the potential for industrial applications of THz spectroscopic and imaging techniques are discussed.
1,636 citations
TL;DR: The current progress of terahertz-wave technologies related to communications applications are examined and some issues that need to be considered for the future of THz communications are discussed.
Abstract: Recent changes in how people consume multimedia services are causing an explosive increase in mobile traffic. With more and more people using wireless networks, the demand for the ultra-fast wireless communications systems is increasing. To date, this demand has been accommodated with advanced modulation schemes and signal-processing technologies at microwave frequencies. However, without increasing the carrier frequencies for more spectral resources, it may be quite difficult to keep up with the needs of users. Although there are several alternative bands, recent advances in terahertz-wave (THz-wave) technologies have attracted attention due to the huge bandwidth of THz waves and its potential for use in wireless communications. The frequency band of 275 ~ 3000 GHz , which has not been allocated for specific uses yet, is especially of interest for future wireless systems with data rates of 10 Gb/s or higher. Although THz communications is still in a very early stage of development, there have been lots of reports that show its potential. In this review, we will examine the current progress of THz-wave technologies related to communications applications and discuss some issues that need to be considered for the future of THz communications.
1,072 citations
TL;DR: A wireless sub-THz communication system near 237.5 GHz with one to three carriers and up to 100 Gbit/s with state-of-the-art active I/Q-MMIC at the Rx is demonstrated.
Abstract: A wireless communication system with a maximum data rate of 100 Gbit s−1 over 20 m is demonstrated using a carrier frequency of 237.5 GHz. The photonic schemes used to generate the signal carrier and local oscillator are described, as is the fast photodetector used as a mixer for data extraction.
1,037 citations
TL;DR: The goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications and report on the reported advantages and challenges of using sub-terahertz andTHz waves as a means to transmit data wirelessly.
Abstract: According to Edholm’s law, the demand for point-to-point bandwidth in wireless short-range communications has doubled every 18 months over the last 25 years It can be predicted that data rates of around 5–10 Gb/s will be required in ten years In order to achieve 10 Gb/s data rates, the carrier frequencies need to be increased beyond 100 GHz Over the past ten years, several groups have considered the prospects of using sub-terahertz (THz) and THz waves (100–2000 GHz) as a means to transmit data wirelessly Some of the reported advantages of THz communications links are inherently higher bandwidth compared to millimeter wave links, less susceptibility to scintillation effects than infrared wireless links, and the ability to use THz links for secure communications Our goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications
991 citations