Tokyo University of Science, Japan

Biography: Yutaka Fukuchi was born in Tochigi, Japan, on April 29, 1975. He received the B.S. and M.S. degrees in electronics engineering from Tokyo University of Science, Chiba, Japan, in 1998 and 2000, respectively, and the Ph.D. degree in electronics engineering from the University of Tokyo, Tokyo, Japan, in 2003.

In 2003, he joined the Department of Electrical Engineering, Faculty of Engineering, Tokyo University of Science, Tokyo, Japan as an Assistant Professor. From 2003 to 2005, he was also a Co-operative Research Fellow in Research Center for Advanced Science and Technology, the University of Tokyo, Tokyo, Japan. Then, he became a Junior Associate Professor of Tokyo University of Science in 2006. Since 2009, he has been an Associate Professor at this university. From 2013 to 2014, he was a Visiting Research Fellow with the High-Speed Optical Communications Group, Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark. His research interests are optical communications, quantum optics, nonlinear optics, and their applications.

Dr. Fukuchi is a member of the Institute of Electrical and Electronics Engineers (IEEE), the Optical Society of America (OSA), and the Institute of Electronics, Information, and Communication Engineers (IEICE).

Speech Title: Characteristics of bismuth-based frequency comb laser

Abstract: Frequency comb lasers (FCLs) with multi-gigahertz spacing are important for many practical applications such as frequency references, multi-wavelength lasers, and coherent waveform syntheses. Good spectral flatness, wide operation bandwidth, high coherence, high efficiency, high stability, and low noise performance are usually required for those FCL applications. Several methods to produce the frequency comb have been proposed and demonstrated in the past. Especially, actively and harmonically mode-locked fiber ring lasers (AHMLFRLs) have become an attractive candidate for the FCLs. The AHMLFRLs generally feature wide tunable wavelength range, short pulse width, small timing jitter, and high repetition frequency. However, it is difficult to produce the frequency comb with good spectral flatness. One of the difficult challenges in the AHMLFRLs is how to produce a spectrally flat frequency comb. Furthermore, the AHMLFRLs commonly use silica-based erbium-doped fibers as the intracavity gain media. Consequently, the tunable wavelength range is limited to the alternative of the conventional wavelength band region or the longer wavelength band region. The tunable wavelength range is also another important issue for the FCLs. In this paper, we review stable, wavelength-tunable, and flat frequency comb generation from a 10-GHz short-cavity AHMLFRL employing a bismuth-based nonlinear erbium-doped fiber with a fiber length of 1.5 m and a bandwidth-variable tunable filter with a rectangular filter profile. The center wavelength can be tuned from 1540 nm to 1620 nm. The comb spectrum can be flatly broadened up to 2.0 nm (250 GHz) with 25 comb lines. The temporal pulse width is around 7 ps. This bismuth-based FCL can maintain stable bit-error-free mode-locking operation throughout the entire wavelength tunable range.

Keywords: Frequency comb, fiber lasers, mode-locked lasers, tunable lasers, Kerr effect