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Proceedings Paper

Electrically tunable laser based on heliconical cholesteric (Conference Presentation)
Author(s): Jie Xiang; Andrii Varanytsia; Fred Minkowski; Daniel A. Paterson; Corrie T. Imrie; Oleg D. Lavrentovich; Peter Palffy-Muhoray

Paper Abstract

STUDENT CONTRIBUTION: Cholesteric liquid crystals (CLC) self-assemble into a periodic supramolecular helical structure with properties of a one-dimensional photonic crystal. The CLCs doped with a fluorescent dye and optical pump enable a distributed feedback cavity and lasing [1]. Although lasing was observed in range of wavelength from near UV to near IR, a practical method of tuning of emission wavelength from a dye-doped CLC without structural destruction of a helix is not demonstrated yet. In this work, we demonstrate an electrically tunable dye-doped CLC laser based on the so-called oblique helicoidal, or heliconical, CLC state [2,3]. In this state, the molecules twist around the helicoidal axis, making an angle smaller than 90 degrees with the axis. Molecular tilt makes the heliconical structure different from the regular CLC (in which the molecules are perpendicular to the axis) and enable electric tunability [2,3]. An electric field applied parallel to the heliconical axis changes the pitch but does not realign the axis. When the field increases, the pitch decreases. As a result, the selective reflection band and a lasing wavelength move towards shorter wavelength. Using heliconical CLC and two laser dyes DCM and LD688, we demonstrate effective tuning of the laser emission wavelength from 574 nm to 722 nm. With appropriate laser dyes, the spectrum can be extended from near UV to near IR. Efficient electric tuning in the broad spectral range and small size of the heliconical cholesteric lasers makes them potentially useful for optical and biomedical applications. [1] P. Palffy-Muhoay, W.Y. Cao, M. Moreira, B. Taheri, A. Munoz, Photonics and lasing in liquid crystal [2] J. Xiang, S.V. Shiyanovskii, C.T. Imrie, O.D. Lavrentovich, Electrooptic Response of Chiral Nematic Liquid Crystals with Oblique Helicoidal Director, Phys Rev Lett, 112 (2014) 217801. [3] J. Xiang, Y.N. Li, Q. Li, D.A. Paterson, J.M.D. Storey, C.T. Imrie, O.D. Lavrentovich, Electrically Tunable Selective Reflection of Light from Ultraviolet to Visible and Infrared by Heliconical Cholesterics, Adv Mater, 27 (2015) 3014-3018.

Paper Details

Date Published: 9 November 2016
PDF: 1 pages
Proc. SPIE 9920, Active Photonic Materials VIII, 99200H (9 November 2016); doi: 10.1117/12.2236345
Show Author Affiliations
Jie Xiang, Kent State Univ. (United States)
Andrii Varanytsia, Liquid Crystal Institute (United States)
Fred Minkowski, Liquid Crystal Institute (United States)
Daniel A. Paterson, Univ. of Aberdeen (United Kingdom)
Corrie T. Imrie, Univ. of Aberdeen (United Kingdom)
Oleg D. Lavrentovich, Kent State Univ. (United States)
Peter Palffy-Muhoray, Kent State Univ. (United States)

Published in SPIE Proceedings Vol. 9920:
Active Photonic Materials VIII
Ganapathi S. Subramania; Stavroula Foteinopoulou, Editor(s)

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