Influence of liquid crystal cladding on light propagation in a tapered optical fiber

摘要

The research is based on properties of a tapered optical fiber, ability to influence external factors on the propagating lightbeam in the fiber and anisotropic properties of the liquid crystal (LC) mixture that surrounds a tapered region. Thecombination of these elements is possible by creating a liquid crystal cell consisting of a layer orientating a liquid crystal(LC) between conductive layers. In that type of a sandwich construction, we can change the orientation of LC moleculesunder influence of the applied electrical voltage. The second interesting feature of LC is change in a structure that resultsfrom the degree of molecules’ alignment. When temperature rises, structure of LC changes from smectic throughnematic to an isotropic liquid. Both the molecules orientation as well as the LC structure changes modified a refractiveindex of structure, which directly affects the propagating light beam in a tapered optical fiber. The spectralcharacteristics in the 500 -1100 nm range for a LC cell filled with a mixture of 1550* oriented orthogonally to the crosssection of the tapered optical fiber are presented. Changes on spectral characteristics depended on manipulation of suchparameters as: electrical voltage (0-200 V), frequency (1-10 Hz), shape of electrical signal, and time course for differentvoltage in the range 20-180 V.