Tadao Nagatsuma

There has been an increasing interest in the application of terahertz (THz) waves to broadband wireless communications. In particular, use of frequencies above 275 GHz is one of the strong concerns among radio scientists and engineers, because these frequency bands have not yet been allocated at specific active services, and there is a possibility to employ extremely large bandwidths for ultra-broadband wireless communications. Introduction of photonics technologies for signal generation, modula

A number of technical breakthroughs in electronics and photonics made since the early 1990s have started to bring terahertz (THz)-wave technologies from laboratory demonstrators to industrial applications such as non-destructive testing, security, medicine, communications, etc. This paper overviews the latest progress in THz-wave technologies in terms of components such as sources and detectors, and system applications, and discusses future challenges towards market developments.

An oscillator which utilizes the effect of the vortex motion in long Josephson tunnel junctions, i.e., flux flow, has been presented in millimeter and submillimeter wave region. An electromagnetic wave generated by the oscillator is detected with a small tunnel junction as a detector with a refined coupling configuration. Quantitative evaluation of the detected power showed that the detected power attained the value of 10−6 W in the frequency range between 100 and 400 GHz, which is far superior

Abstract There has been an increasing interest in photonic generation of RF signals in the millimeter‐wave (30 GHz∼300 GHz) and/or terahertz‐wave (0.1 THz∼10 THz) regions, and photodiodes play a key role in it. This paper reviews recent progress in the high‐power RF photodiodes such as Uni‐Traveling‐Carrier‐Photodiodes (UTC‐PDs), which operate at these frequencies. Several approaches to increasing both the bandwidth and output power of photodiodes are discussed, and promising applications to bro

This paper reviews a recent progress in terahertz wireless communications enabled by photonics technologies. After briefly summarizing transceiver configurations with electronics and photonics technologies, photonics-based approaches to achieving over 100-Gbit/s data rates are discussed. Then, some of our updated results on real-time wireless transmission experiments using discrete components are shown at data rates up to 50 Gbit/s. Finally, integration technologies are described by demonstratin

A theoretical study is made of a travelling-wave-type oscillator, which utilizes a flux flow in a long Josephson junction for use as a local oscillator in the integrated superconducting receiver system. An internal electromagnetic field of the oscillator junction in the flux-flow state is investigated both numerically and analytically. It is shown that the voltage amplitude of the internal oscillation increases gradually in the direction of the flux flow and reaches a maximum value at the juncti

Numerical as well as experimental studies have been made of the oscillation stability for the travelling-wave-type oscillator, which utilizes a vortex motion in a long Josephson junction, i.e., a flux flow. For the Josephson oscillator, a steep current step in a dc I-V characteristic improves the oscillation stability. Two kinds of effects which degrade the steepness of the current step have been investigated for the long junction of the overlap geometry. One is the self-field effect which makes

This paper describes continuous millimeter-wave and terahertz (THz)-wave applications, where telecom-based photonics technologies are efficiently employed to enhance their performance. First, 300-GHz-band wireless communications are described toward real-time error-free transmissions at 50 Gbit/s and beyond. Next, a novel approach to increase a phase measurement sensitivity in THz frequency-domain spectroscopy systems is explained, and a similar technique is successfully applied to the visualiza

Three-dimensional (3D) terahertz (THz) imaging or THz tomography has recently proven to be useful for nondestructive testing of industrial materials and structures. In place of previous imaging techniques such as THz pulsed/continuous-wave radar and THz computed tomography, we propose a THz optical coherence tomography using photonics- and electronics-based THz sources, and demonstrate thickness measurement and tomographic imaging in frequency regions from 400 to 800 GHz.

An error‐free wireless transmission of a 9 Gbit/s on–off keying modulated signal as well as a 4 k video signal is demonstrated using resonant tunnelling diodes as active elements in both the transmitter and the receiver. The employed system and the modulation scheme enabling the high data rate are discussed.