University of Electro-Communications

About: University of Electro-Communications is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Laser & Robot. The organization has 8041 authors who have published 16950 publications receiving 235832 citations. The organization is also known as: UEC & Denki-Tsūshin Daigaku.

ULF geomagnetic field measurements in Japan and some recent results associated with Iwateken Nairiku Hokubu earthquake in 1998

Abstract: Previous studies on Spitak, Loma Prieta, and Guam earthquakes indicate that large earthquakes were accompanied by preceding magnetic anomalies. In order to confirm these facts and to investigate ULF phenomena in details, a network of ULF magnetometers has been installed in Japan. Network observations including small arrays have been carried out. Also, the geomagnetic data observed at Matsukawa station associated with Iwateken Nairiku Hokubu earthquake (M6.1, September 3, 1998, depth 10 km) are presented. 4.5 years data have been analyzed and the obtained result is discussed. The variation of spectral density ratio between the horizontal and vertical components (polarization) exhibits an anomalous behavior two weeks before the earthquake. This is a unique change discovered from the rather long-term analysis, which suggests that this anomalous change might be a possible signal associated with the earthquake preparation phase.

Optical frequency-domain imaging microprofilometry with a frequency-tunable liquid-crystal Fabry-Perot etalon device.

Abstract: An optical frequency-domain interference microscope with a liquid-crystal Fabry–Perot interferometer as an optical frequency-scan device was developed for microscopic three-dimensional shape measurements. The proposed system can perform absolute measurement of the discontinuous surface profile of a microscopic object without use of mechanically moving components such as a piezoelectric transducer or a grating spectrometer. Experimental results are presented that demonstrate the validity of the principle.

Construction of KAGRA: an Underground Gravitational Wave Observatory

Abstract: The major construction and initial-phase operation of a second-generation gravitational-wave detector, KAGRA, has been completed. The entire 3 km detector is installed underground in a mine in order to be isolated from background seismic vibrations on the surface. This allows us to achieve a good sensitivity at low frequencies and high stability of the detector. Bare-bones equipment for the interferometer operation has been installed and the first test run was accomplished in March and April of 2016 with a rather simple configuration. The initial configuration of KAGRA is called iKAGRA. In this paper, we summarize the construction of KAGRA, including a study of the advantages and challenges of building an underground detector, and the operation of the iKAGRA interferometer together with the geophysics interferometer that has been constructed in the same tunnel.

Synchronization of feedback-induced chaos in semiconductor lasers by optical injection

Abstract: In this paper, synchronization of chaotic oscillations in semiconductor lasers by optical injection in a transmitter-receiver configuration is studied numerically. A chaotic signal is generated from a semiconductor laser with optical feedback in the transmitter and is injected into the receiver laser without optical feedback. We examined the conditions of chaotic synchronization in the system. As a result, we observed complete chaos synchronization within a finite area of very small parameter mismatch between the two laser systems. In addition, chaotic oscillation synchronized by amplification phenomena was observed in the ordinary injection-locking regime with higher optical injection ratios. We demonstrated that synchronization of chaotic oscillations by amplification results from a kind of injection locking under chaotic light injection and is very tolerant to the parameter mismatch between the two lasers, in contrast to the complete synchronization case.