韩国首尔大学Ju Han Lee 教授学术报告(2)

来源:信息科学与技术学院  作者:叶佳  日期:2018-08-22  点击数:354

韩国首尔大学Ju Han Lee 教授学术报告(2)


报告题目:Topological Insulators for 2-μm Ultrafast Fiber Lasers

报 告 人:Ju Han Lee 教授(首尔大学)

报告时间:2018年8月23日(星期四) 15:00

报告地点:犀浦校区X9511

主 持 人:闫连山教授


报告内容:

In the past decade, one of the main subjects in condensed-matter physics has been topological insulators (TIs), which possess extraordinary charge and spin properties on their edges and surfaces. TIs feature gapless metallic states on the surface due to the combination of strong spin-orbit coupling and time-reversal symmetry, even if they exhibit insulating energy gaps in the bulk of the material. A 2-dimensional (2D) topological insulator exhibiting the quantum spin Hall effect without an external magnetic field was experimentally realized in HgTe quantum well structures by König et al. in 2007. TI materials such as Bi1-xSbx, Bi2Se3, Bi2Te3, and Sb2Te3 were confirmed to have the topological band structures. Since TIs possess unique electronic properties, they are considered as a promising material platform for spintronic and quantum computing devices. In 2012, Bernard et al. opened the way to use a new Dirac material for photonic applications as a nonlinear saturable absorber. Since then, a number of investigations on the use of TI-based saturable absorbers for mode-locking or Q-switching were carried out. The combination of the small bandgap bulk (0.2 to 0.3 eV) and the gapless surface enables TIs to possess an ultra-broad bandwidth of saturable absorption operation. In this presentation I review our group’s recent investigation results on the use of  saturable absorbers based on bulk-structured TIs for the implementation of pulsed fiber lasers in the 2 μm spectral region. It is shown that Q-switched or mode-locked pulses can readily be produced from Thulium fiber-based cavities incorporating TI-based saturable absorbers. Unlike the TI-based saturable absorbers demonstrated by other groups, which were based on nanosturctures, we used a bulk-structured, thick TI layer rather than an ultrathin nanosheet-based layer due to ease of fabrication, and we demonstrated that a bulk-structured, micrometer-thick TI film can readily act as an efficient 2 μm saturable absorber.

报告人简介:

Ju Han Lee 教授是国际知名的非线性光学和光信息处理及传感专家。至今已发表了200多篇论文,包括20篇国际会议特邀报告。曾担任IEEE光子学会GOLD委员会主席,现担任韩国光学学会(KOS)国际关系主任(Director of International Relations, 2012-),并先后在10多个国际会议(包括OFC、OECC、ACP等)担任TPC委员。Lee教授曾经获得IEEE LEOS Graduate Fellowship(2002);美国光学学会NewFocus Student Award(2003)以及日本JSPS学者(2004)等。


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