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With thermotropically rod-like nematics such as 5CB in particular, liquid crystals (LCs) have been shown to be potentially applicable to biological sensing or label-free immunodetection thanks to their unique birefringent, anchoring, alignment, and collective properties. For such a LC-based biosensing technique to be promising, good performance, as manifested by the resulting sensitivity and specificity, must be demonstrated. In order to warrant desired high sensitivity, various methods can be simultaneously adopted in the sample fabrication procedure.

In the first part of this colloquium, I shall report on our recent development of various approaches toward ultrahigh sensitivity in nematic-based immunoassays for potential clinical applications. The approaches entail (1) a new concept of selection of the sensing mesogen; (2) an unconventional method for antibody–antigen reaction; (3) the surface modification of the surfactant layer for LC alignment. This technique relies on conventional polarizing optical microscopy and the study itself involves the contact-angle measurement and Fourier-transform infrared spectroscopy. Special attention will be paid to the conspicuousness of the optical texture varying with the cancer biomarker CA125 antibody/antigen concentration and to the extent of surface modification of the aligning layer on the substrate as revealed by the hydrophilicity data.

Moreover in the second part of the colloquium, LC photonics beyond texture observations or the use of chiral agents instead will be discussed for biosensing purposes. These new methods, very recently developed in this laboratory and proven to be more advantageous, are based on the measurements of voltage–transmittance curves as well as voltage-dependent electric capacitance for nematic cells and visible spectra of cholesteric liquid crystals.

第二场报告：9月18号（周五）下午3:30-5:00

地点：澳门太阳娱乐网站官网力学楼434会议室

题目：Liquid-crystal multichannel and laser devices based on 1-D photonic bandgap structures

Wei Lee

Institute of Imaging and Biomedical Photonics, College of Photonics

National Chiao Tung University, Tainan 71150, Taiwan

报告内容摘要：

Incorporation of liquid crystal (LC) as a defect layer in a photonic crystal (PC) permits the optical transmission spectrum of defect modes to be magnetically or electrically tunable within the photonic bandgap. This feature of tunability makes the PC/LC hybrid structure potential for designing various types of optical devices. Recently, we have demonstrated several distinctive photonic bandgap structures based on one-dimensional (1-D) PCs containing memory-incapable or memory-enabling LC as a defect layer. The optical state remains unchanged in the memory state after removal of applied voltage. Due to the wavelength tunability, transmission adjustability and optical multistability of the defect modes, these 1-D hybrid structures are alluring for photonic device applications such as low-power-consumption multichannel filters, light shutters or electrically controllable intensity modulators without any polarizers.

In this presentation, our development of various PC/LC structures for photonic applications will be presented. Special attention will be paid to lasing from 1-D photonic bandgap structures impregnated with a dye-doped LC layer. An asymmetric photonic bandgap structure will be explored in a case study where dye-doped nematic LC is employed to generate ultralow-threshold, single-mode lasing. Moreover, I shall highlight the realization of color-switchable and white-light laser devices along this line using unconventional dielectric mirrors for the hybrid photonic bandgap structure.

报告人简介：

[OSA] Wei Lee received his M.S. degree in electro-optical engineering from National Chiao Tung University (NCTU), Taiwan, in 1987 and his Ph.D. degree in physics from the University of Alabama at Birmingham (UAB), AL, in 1993. He was a lecturer in the Department of Physics at UAB from 1993 to 1994 and worked as a visiting assistant professor of physics and astronomy at the University of Toledo, OH, between 1994 and 1997. As a faculty member through the ranks of Assistant Professor (1997–2002), Associate Professor (2002–2005), and Full Professor (2005–2012), Dr. Lee was affiliated with the Department of Physics and Center for Nanotechnology at Chung Yuan Christian University, Taiwan, from August 1997 through January 2012. During this period of time, he took his sabbatical leave as a visiting professor of optics at CREOL, the College of Optics and Photonics of the University of Central Florida, FL, between 2009 and 2010, and a visiting scholar at the L. V. Kirensky Institute of Physics, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences, Russia in 2010. He served as Director of the Institute of Imaging and Biomedical Photonics, College of Photonics, National Chiao Tung University, Tainan Campus, Taiwan, between February 2012 and July 2015 and is the President of Taiwan Liquid Crystal Society. He has worked in the research areas of liquid-crystal (LC) optics, structural vibration analysis, laboratory astrophysics, physics education, and pedagogy of English for science and technology for non-native speakers since 1985. His recent research interests focus on LC photonic and dielectric properties, photonic crystals, and LC-based biosensing. He has served on the editorial board for the Optical Society (OSA) journal Optical Materials Express since it was launched in May, 2010.

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