Electrically tunable laser based on oblique heliconical cholesteric liquid crystal

Jie Xiang, Andrii Varanytsia, Fred Minkowski, Daniel A. Paterson, John M D Storey, Corrie T. Imrie, Oleg D. Lavrentovich*, Peter Palffy-Muhoray

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

135 Citations (Scopus)
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Abstract

A cholesteric liquid crystal (CLC) formed by chiral molecules represents a self-assembled one-dimensionally periodic helical structure with pitch p in the submicrometer and micrometer range. Because of the spatial periodicity of the dielectric permittivity, a CLC doped with a fluorescent dye and pumped optically is capable of mirrorless lasing. An attractive feature of a CLC laser is that the pitch p and thus the wavelength of lasing λ can be tuned, for example, by chemical composition. However, the most desired mode to tune the laser, by an electric field, has so far been elusive. Here we present the realization of an electrically tunable laser with λ spanning an extraordinarily broad range (>100 nm) of the visible spectrum. The effect is achieved by using an electric-field-induced oblique helicoidal (OH) state in which the molecules form an acute angle with the helicoidal axis rather than align perpendicularly to it as in a field-free CLC. The principal advantage of the electrically controlled CLCOH laser is that the electric field is applied parallel to the helical axis and thus changes the pitch but preserves the single-harmonic structure. The preserved single-harmonic structure ensures efficiency of lasing in the entire tunable range of emission. The broad tuning range of CLCOH lasers, coupled with their microscopic size and narrow line widths, may enable new applications in areas such as diagnostics, sensing, microscopy, displays, and holography.

Original languageEnglish
Pages (from-to)12925-12928
Number of pages4
JournalPNAS
Volume113
Issue number46
Early online date2 Nov 2016
DOIs
Publication statusPublished - 15 Nov 2016

Bibliographical note

Acknowledgments
We are grateful to V. A. Belyakov and S. V. Shiyanovskii for useful discussions and to G. Cukrov for the measurements of refractive indices. CB9CB was synthesized by the Organic Synthesis Facility at the Liquid Crystal Institute, Kent State University. This work was supported by National Science Foundation DMR 1410378.

Keywords

  • Cholesteric liquid crystals
  • Electric tunability
  • Heliconical structure
  • Lasing

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