Tunable Optical Waveguide Devices Via Liquid Crystals

In recent years,with the continuous progress of integrated optics,more and more attention has been paid to tunable integrated optics technology.By changing the refractive index of materials,the propagation intensity,wavelength and mode can be varied.Liquid crystals(LCs)are tunable optical materials with excellent performance and optical anisotropy.Based on the optical anisotropy,the refractive index variation through a uniform medium is achieved to support the total internal reflection.Due to the tunability of LCs,the response of LC waveguides to various external fields is realized.This thesis aims to provide a new strategy not only for the development of high-performance,low-cost tunable integrated optics in a variety of external fields and flexible integrated optics but also for the design,fabrication and characterization of LC waveguides.The major research results are summarized as follows:1.Here,versatile graded-index waveguides are realized through presetting the inplane variant LC directors.They exhibit pronounced polychromatic light-guiding performance and their performances match well with simulations.Then,the propagation properties of liquid crystal waveguides are claimed by means of numerical analysis.The propagation loss of red light can be 1.68 d B/mm.Meanwhile,we explore the reasons for the propagation loss change at different wavelengths.Herein,we take the bending waveguide and the ring resonator as instances to verify the arbitrary manipulation of light propagation.It paves the way to the development of LC integrated optics.Compared with traditional waveguides,the convenient photopatterning process facilitates their arbitrary design,low cost and diverse functionality.It provides a new solution for the development of waveguides.2.Thanks to their optical anisotropy and intrinsic external-stimuli responsivity,the polarization tunability and thermal switchability are verified.For polarization dependent and thermotropic LC,changing incident polarization direction or raising the temperature makes the material optical isotropic,thus the light guiding effect vanishes.The liquid crystal polymer film is transferred from the rigid silica to a flexible film,thus a flexible LC waveguide is obtained.By selectively polymerizing,robust functional components and active connecting waveguides could be realized on the same chip.It also makes flexible tunability of integrated waveguides possible.Highresolution patterned photoalignment technology ensures the arbitrary design and diverse functionality.