講演題目：Speaker 1: Prof. Mads Lonstrup Nielsen
Research Center COM, Technical Univ. of Denmark, Copenhagen, Denmark
Title 1: Experimental and theoretical investigation of semiconductor optical amplifier based all-optical switches
Speaker 2: Prof. Guoquan Zhang,
Photonics Research Center, School of Physical Sciences, Nankai University, China
Title 2: Ultraslow light propagation and spatial solitons in photorefractive nonlinear media
（フォトリフラクティブ非線形媒質中における極緩光速度伝搬と空間ソリトン）
日時：Tuesday July 20th, 2004, 10am-12am
場所：Seminar Room: E6-803 (Room 803, 8th floor of East-6 Bldg., phone: 3480)
対象： 教職員、大学院生、卒研生など
講演者１紹介：
Dr. Mads Nielsenはデンマーク工科大学のResearch Center COM研究所の
OptoelectronicsグループやNetworkグループで超高速半導体光ゲート研究に
従事してきた新進気鋭の若手研究者であり、半導体超高速光学緩和現象の
先駆的研究で知られるProf. Jesper Morkらの強い推薦により本学に
招聘しました（7月上旬〜8月中旬）。
Research Center COM研究所は、スイス工科大学、Heinrich-Herz研究所、
Alcatel研究所、BT研究所とともに90年代前半から現在に続くRaceやActsなど
欧州大型光通信プロジェクトで常に主導的役割を果たしてきた光通信研究拠点です。
米UCSB、米Lucent研究所、東工大、国内企業研究所とも活発な人材交流を
継続しています。
講演１概要：
The factors governing the modulation bandwidth of Semiconductor
Optical Amplifiers (SOAs) are reviewed, and schemes for reducing
detrimental patterning effects are discussed. Three types of SOA-based
switches are investigated numerically: so-called standard-mode and
differential-mode switches, and the filtering-assisted switch.
Differential -mode switches are shown to eliminate one contribution
to the patterning effects, referred to as the linear patterning. This
enables operation at bitrates far beyond the limit set by the carrier
lifetime, but ultimately a saturation-induced patterning effect,
nonlinear patterning, is found to limit the performance. Two
implementations of differential-mode switches, the Mach-Zehnder
interferometer (MZI) and the delayed-interferometer signal converter
(DISC), are compared at bitrates up to 160 Gb/s, and fundamental
differences are demonstrated.
A new optical spectrum approach to small-signal analysis is
presented, and is used to assess the bandwidth enhancing effect of
different optical filters, as well the impact of the filter phase
response. Experiments at up to 80 Gb/s verify the predictions of the
small-signal analysis.
講演者２紹介：
Guoquan Zhang教授は中国南開大学フォトニクス研究センターにおいて
フォトリフラクティブ非線形光学の研究に従事されており、４年前には
日本学術振興会外国人特別研究員として２年間本学に滞在されています。
今年の６月から７月にかけてCOE招聘研究員として共同研究のため本学に
滞在されており、この機会に最近の研究に関するセミナーをお願いし
ました。皆様のご参加を歓迎致します。
講演２概要：
In this talk the dispersive properties of the photorefractive
two-wave mixing process will be discussed. Such a highly dispersive
wave mixing process was proposed to slow down the group velocity of
lights. Ultraslow light propagation with a group velocity as low as
0.06 m/s was demonstrated. In addition, photorefractive nonlinearity
was shown to be able to compensate the diffraction effect of light
and to generate spatial solitons. Self-trapping of both coherent and
incoherent dark notches were demonstrated in photorefractive media.
Several applications of photorefractive spatial solitons were
demonstrated. Features of and recent progress on photorefractive
spatial solitons will be discussed.
Organizers: Graduate school of EE, Yoshiyasu Ueno (5807), Yasuo Tomita (5164)
問合せ先： 電子工学専攻 上野芳康(5807)、富田康生(5164)
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