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.

Tunable noise-like pulse generation in mode-locked Tm fiber laser with a SESAM.

Abstract: We report on a tunable noise-like pulse (NLP) generation in a mode-locked Tm fiber laser with a SESAM. A tuning range of 1895-1942 nm, while keeping the spectral bandwidth of 10-19 nm under NLP mode-locked operation, was obtained by a tunable filter based on chromatic dispersion of telescope lenses. At the center wavelength of 1928 nm, the maximum output power of 195 mW with the spectral bandwidth of 18.9 nm was obtained. The repetition rate was 20.5 MHz and the corresponding pulse energy was 9.5 nJ. To our knowledge, this is the first report of a tunable NLP mode-locked laser based on chromatic dispersion of a lens system.

Effects of Antenna Switching on Band-Limited Spatial Modulation

Abstract: In this letter, we investigate the effects of antenna switching on band-limited spatial modulation (SM), where the employment of an SM-specific practical time-limited shaping filter is taken into account. More specifically, we evaluate the SM scheme's performance penalty imposed on a bandwidth efficiency, which arises due to the time-limited pulse transmissions. Furthermore, to combat this limitation while maintaining lower RF chains than transmit antenna elements, we propose a multiple-RF antenna switching operation that allows us to exploit a longer pulse shape than that enabled by a single-RF SM scheme. It is demonstrated in our simulations that upon increasing the number of transmit antenna elements, the SM scheme is capable of outperforming the classic MIMO systems, under the assumptions of a low number of RF chains and realistic pulse shaping.

In-plane magnetic field dependence of electric field-induced magnetization switching

Abstract: Electric field-induced magnetization switching through magnetization precession is investigated as a function of in-plane component of external magnetic field for a CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis. The switching probability is an oscillatory function of the duration of voltage pulses and its magnitude and period depend on the magnitude of in-plane magnetic field. Experimental results are compared with simulated ones by using Landau-Lifshitz-Gilbert-Langevin equation, and possible factors determining the probability are discussed.

Temporal contrast enhancement of femtosecond pulses by a self-diffraction process in a bulk Kerr medium

Abstract: We demonstrated for the first time the application of a self-diffraction (SD) process in a bulk Kerr medium to improve the temporal, spectral, and spatial qualities of femtosecond laser pulses. A proof-of-principle experiment succeeded in improving the temporal contrast of a femtosecond pulse by four orders of magnitude even in the picosecond region using a 0.5-mm-thick fused silica glass plate by this technique. The energy conversion efficiency from the incident pulses to the two first-order SD signals is about 12%. By the SD process, a laser pulse with smoother spectral shape, higher beam quality, and shorter pulse duration than those of the input pulse was generated. This technique is expected to be used to design background-free petawatt laser system in the future.