Browsing by Author "Shen, Dong"

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A thermally tunable narrowband selector based on a chiral nematic containing a binary thermosensitive chiral dopant mixture
(2017-01-01)
Yang, Zong-Han
;
Hsiao, Yu-Cheng
;
Shen, Dong
;
Lee, Wei
;
光電系統研究所
We employed a thermosensitive chiral dopant (CD), characterized by its thermoinduced change in helical twisting power (HTP) in terms of the handedness and strength, to shift the Bragg reflection band of a CLC. A thermally tunable photonic bandgap (PBG) device was demonstrated using a one-dimensional asymmetric photonic crystal (PC) infiltrated with the CLC as a defect layer. With a temperature controller to shift the PBG of the CLC, two narrow transmission bands can be tuned in the spectrum dominated by the asymmetric PC structure. This optical device can find applications as a tunable narrowband wavelength selector or an intensity controller.
Red, Green, and Blue Reflections Enabled in an Electrically Tunable Helical Superstructure
(2018-03-05)
Hsiao, Yu-Cheng
;
Yang, Zong-Han
;
Shen, Dong
;
Lee, Wei
;
光電學院
Materials with tunable optical properties in the visible spectrum are intriguingly important in science and technology. Such desired tunability can be conveniently accomplished by controlling optical materials with electric field. Now an organic film of self-organized helical superstructure producing electrically tunable reflection of visible light is introduced in this work. The composite is a dual-frequency thermosensitive cholesteric (DFTC) material consisting of a liquid crystal host doped with a binary chiral-dopant mixture including a thermosensitive chiral switch. The red, green, and blue reflections in the DFTC film can be obtained by varying the frequencies of a 45 V-rms applied voltage to induce dielectric heating. The resulting variation in temperature and, in turn, in helical pitch length, enables various wavelengths of reflection to render full-color display in a single film without the need of film stacking. As far as it is known, this is the first work to demonstrate broad electrical tuning of cholesteric reflection in red, green, and blue.