ILCS

Jie Xiang received his Bachelor degree in Optoelectronic engineering (2007), and Master degree in Instrument Science and Technology (2009) from Harbin Institute of Technology, China. He is currently a Ph.D. candidate in Liquid Crystal Institute and Chemical Physics Interdisciplinary Program (Kent State University, USA), performing research under the supervision of Prof. Oleg. D. Lavrentovich. His research interests include liquid crystal optical metamaterials; blue phases, cholesteric, and twist bend nematics liquid crystals, and their electro-optic applications.

Real-time video (Quicktime plug-in required) demonstrates the electrically tunable selective reflection of light by an oblique helicoidal (heliconical) structure of a cholesteric under an AC electric field. In the heliconical structure, the director orientation with respect to the helicoidal axis is oblique, rather than perpendicular, as in a regular cholesteric. Because of the non-vanishing projection of the director onto the axis, the electric field, acting along the axis, realigns the molecules along itself and thus changes the pitch without reorienting the helicoid axis (for more details, see J. Xiang et al, Adv. Mat. 2015, DOI: 10.1002/adma.201500340). The reflected color continuously changes from ultraviolet to deep blue, then green, yellow, red and, finally, to the infrared, when the electric field varies from 1.7V/µm to 0.7V/µm the demonstrated spectral sweeping occurs within 20 sec. The experiment was performed at 25°C. The horizontal extension of the video area is 260 µm

More details about Jie’s research interests and also the research group can be found in http://lavrentovichgroup.com/xiang.html
Jury comment: Heliconical cholesterics are an extraordinary class of materials that have received significant attention since the discovery of their unique structure. The tuning of the wavelength of the selectively reflected light all the way from the UV to the infrared is most remarkable as can be seen in the winning movie clip.