"Tri-refringence, Superprisms, and Pulses-on-the-fly in Photonic Crystal Waveguides"
Prof. Jeremy J. Baumberg
Oct 28, 2003
講演題目： Tri-refringence, Superprisms, and Pulses-on-the-fly in Photonic Crystal Waveguides
講 師 ： Prof. Jeremy J. Baumberg
(Department of Physics & Astronomy, University of Southampton, and Mesophotonics Ltd., Chilworth Science Park,Southampton, S016 7NP, UK)
日 時 ： 平成15年10月28日 (火) 17:00-
場 所 ： 北海道大学大学院工学研究科 量子物理工学専攻会議室 A3-62
要 旨 ：
Photonic Crystal Waveguides promise novel optical functionality in a wide variety of ways due to the considerable modification in optical propagation and interactions induced in these sub-micron periodic structures. Using planar silicon-compatible processing we have produced a wide variety of nanostructured devices over the past few years [1-8] that exhibit high quality photonic bandgap and photonic crystal features. In particular we have gained an understanding of such devices of ultrawide bandwidth ranges allowing us to provide systematic comparison with a variety of our modelling techniques. Recently we have explored how light propagates through photonic crystals by directly tracking the temporal delay of each wavepacket component [1]. In this talk we will discuss a number of the features of photonic crystal waveguides that we are investigating.
[1] "Separation of Photonic Crystal Waveguides Modes using Femtosecond Time-of-Flight", M. C. Netti, C. Finlayson, J. J. Baumberg et al. Appl. Phys. Lett. 81, 3927 (2002).
[2] "Optical Trirefringence in Photonic Crystal Waveguides", M.C. Netti, A. Harris, J.J. Baumberg et al., Phys. Rev. Lett. 86, 1526 (2001).
[3] "Complete and absolute photonic bandgaps in highly symmetric photonic quasicrystals embedded in low refractive index materials", M.E. Zoorob et al., Mat.Sci.Eng.B 74, 168 (2000).
[4] "Experimental investigation of photonic crystal waveguide devices and line-defect waveguide bends", M.D.B. Charlton et al., Mat.Sci.Eng.B 74, 17 (2000).
[5] "Complete photonic bandgaps in 12-fold symmetric quasicrystals", M.E. Zoorob, M.B.D. Charlton, G.J. Parker, J.J. Baumberg and M.C. Netti, Nature 404, 740 (2000).
[6] "Visible Photonic Bandgap Engineering in Silicon Nitride Waveguides", M.C. Netti, M.B.D. Charlton, G.J. Parker, J.J. Baumberg, Appl. Phys. Lett. 76, 991 (2000).
[7] "Guided mode analysis, and fabrication of a 2-dimensional visible photonic band structure confined within a planar semiconductor waveguide", M.D.B. Charlton et al., Mat.Sci.Eng.B 49, 155 (1997).
[8] "Ultra-Broadband Transmission Measurements on Waveguides of Silicon-Rich Silicon Dioxide", RT Neal, CE Finlayson, MC Netti, MDCCharlton, GJ Parker, JJ Baumberg, Appl. Phys. Lett. (2003).
世話人 松田 理
（omatsuda@eng.hokudai.ac.jp)
北海道大学大学院工学研究科
"LC PHASES FORMED BY BANANA-SHAPED MOLECULES POSSIBLE CONSEQUENCES OF TETRAHEDRATIC ORDER"
Prof. Helmut R. Brand
Oct 14, 2003
講演題目： LC PHASES FORMED BY BANANA-SHAPED MOLECULES POSSIBLE CONSEQUENCES OF TETRAHEDRATIC ORDER
講 師 ： Prof. Helmut R. Brand
(Theoretische Physik III, Universitat Bayreuth, 95440 Bayreuth, Germany)
日 時 ： 平成15年10月14日 (火) 11:00-
場 所 ： 北海道大学大学院理学研究科物理学専攻 大学院講義室 理学部 2号館（2－11号室）
要 旨 ：
Some of the most interesting developments in liquid crystals over the last few years are related to the physical properties of the liquid crystalline phases exhibited by banana-shaped (bent-core) molecules.
Experimental evidence to date suggests that this is indeed a new sub-field of thermotropic liquid crystals. The biggest challenge is the condensed state known as B7 that grows into the isotropic liquid with many different growth patterns including spirals with both hands. Neither the symmetry nor the physical properties of B7 are understood. A tetrahedratic phase, T, is described by four unit vectors, n1 to n4, oriented along the four tetrahedral corners of a cube. It has the symmetry:
T (- na) = - T ( na) (a = 1,2,3,4);
that is odd under parity. As tetrahedra are not space-filling objects, they can be viewed equally well as precursors of condensed lamellar and/or columnar mesophases. Tetrahedratics are thus a model for studying frustrated lamellar and columnar liquid crystalline phases with many different condensed states that are energetically very close together. In a first step we analyzed the coupling of flow to electric fields and temperature gradients assuming that the symmetry of the tetrahedratic phase is unchanged by the external forces. We also discuss what happens when the tetrahedral angle is allowed to change under the influence of external forces and fields. We also analyze how an external electric field applied to an isotropic tetrahedratic phase can induce orientational order Qij as well as smectic layering. The relation of our analysis to recent experimental observations by Weissflog et al. will be discussed. Work done in collaboration withP.E. Cladis and Harald Pleiner
世話人 北 孝文
（kita@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科
「有機超伝導体の量子渦糸状態」
佐々木 孝彦 氏
Oct 02, 2003
講演題目： 有機超伝導体の量子渦糸状態
講 師 ： 佐々木 孝彦 氏
(東北大学・金属材料研究所・助教授)
日 時 ： 平成15年10月2日 (火) 16:30-
場 所 ： 北海道大学大学院理学研究科物理学専攻 大学院講義室 理学部 2号館 4階 9号室 (2-4-09)
要 旨 ：
酸化物高温超伝導体における渦糸状態の研究により第２種超伝導体の渦糸に関する理解が飛躍的に進歩した．その中でも新しい渦糸相とその相転移が明らかにされてきた．このような渦糸物理は，高温超伝導体にのみ固有ではなくゆらぎの大きい２次元系であれば他の物質系でも統一的に理解，観測されるはずである．さらに新たな物質パラメーターを有する系では新奇な渦糸物理の展開が期待される．有機超伝導体は超伝導転移温度は約１０Kと低いが，大きな２次元異方性，低キャリア密度などゆらぎ効果が顕著な系である．また極めてクリーンな電子系を有し，磁気量子振動効果による詳細な電子状態研究が可能な系でもある．このような特徴を有する有機超伝導体の渦糸状態に関する現状をレビューし，最近，我々が見出した「新渦糸状態-量子磁束スラッシュ-」と「渦糸状態での磁気量子振動効果」について紹介する．
世話人 松永 悟明
（mat@phys.sci.hokudai.ac.jp)
北海道大学大学院理学研究科
