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Integrated Bragg reflectors in low-index media: Enabling strategies for wavelength tunability in electro-optic liquid crystals

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
Article number071108
JournalOptical Engineering
Issue number7
Publication statusPublished - Jul 2011
Publication typeA1 Journal article-refereed


This paper reports two configurations of Bragg reflectors based on liquid crystals confined between two small glass plates. Both approaches employ the efficient electro-optic effect in liquid crystals, which allows tunability of the reflectors by using low voltages. The molecular reorientation induced by an applied electric field implies a refractive index modulation seen by polarized light propagating into the liquid crystal. We show design criteria and profile optimization of the electrodes to induce a liquid crystal refractive index periodic modulation, providing a wavelength selective propagation of confined light in the liquid crystal. The two proposed device configurations differ for the top-bottom electrode configuration in one case and coplanar electrodes in the other case. Modeling of both configurations has been carried by calculating the applied electric field distribution and its interaction with the liquid crystal elastic properties taking into account the boundary conditions due to the alignment layer on the inner faces of the glass substrates. The calculated performance in terms of high wavelength selectivity and ultrawide spectral tuning range indicate that the two designed structures can be proposed for both optical filtering and to produce novel low power integrated distributed feedback resonators in dense wavelength division multiplexed fiber optic systems.


  • Bragg gratings, Electro-optics, Integrated optics, Liquid crystals, tunable filters, Waveguides