Prof. Shinji Yamashita
Tokyo University

We recently proposed and demonstrated a saturable absorber (SA) incorporating Carbon nanotube (CNT). CNT-based SA offers several key advantages such as: ultra-fast recovery time, polarization insensitivity, high optical damage threshold, mechanical and environmental robustness, chemical stability, small size, compatibility to optical fibers and the ability to operate at wide range of wavelength bands. Using the CNT-based SA, we have realized femtosecond fiber pulsed lasers not only at 1550nm wavelength band, but also 1300nm and 1000nm bands. Taking the advantages of small size and compatibility to optical fibers, we also realized the very short- cavity (~2cm) femtosecond fiber pulsed lasers having high repetition rate (5GHz).

Besides the saturable absorption, CNT has been shown to have high third-order Kerr nonlinearity, which is also attractive for realization of compact and integrated functional photonic devices, such as all-optical switches and wavelength converters. We have already demonstrated wavelength conversion of 10Gb/s signal using the cross-polarization modulation in the CNT device through the Kerr nonlinearity.

In this talk, we first present photonic properties of CNTs, and review our studies on CNT-based mode-locked fiber lasers, and show our recent research progresses on novel photonic devices using evanescent coupling between optical field and CNT. We also refer to fabrication methods of CNT-based photonic devices.

Shinji Yamashita received the B.E. degree in electrical engineering and the M.E. and Dr. Eng. degrees in electronic engineering from the University of Tokyo, Tokyo, Japan, in 1988, 1990, and 1993, respectively. In 1991, he was appointed as a Research Associate, and in 1994, he became a Lecturer at the Research Center for Science and Technology (RCAST), University of Tokyo. Since 1998, he has been an Associate Professor in the Department of Electronic Engineering, Faculty of Engineering, University of Tokyo. From 1996 to 1998, he was a Visiting Research Fellow with the Optoelectronics Research Center (ORC), University of Southampton, Southampton, U.K. He has been engaged in research of coherent optical fiber communications and optical fiber amplifiers and lasers. His current research interest is in active and passive fiber devices for optical fiber communications and sensors. Dr. Yamashita is a Member of IEEE and the Institute of Electronics, Information, and Communication Engineers (IEICE) of Japan.