In this work we present theoretical and experimental results of influence of electric field on reorientational nonlinearity in homeotropic oriented nematics. In the analyzed configuration the light beam passing through the liquid crystalline layer induces the reorientation, which is observed in far-field diffraction pattern changes as a result of self-modulation effect. The created phase mask inside the nematic cell can be used in optical switching or to control the propagating direction of optical signals passing through the liquid crystalline cell. Both electric and optical field control the observed phase pattern dynamics. The response time in reorientational phenomena is large and its determination and reducing is very important issue for applications. Obtained results are in good agreement with theoretical prediction.
Liquid crystals are very important anisotropic materials in modern optoelectronics. Among other unique properties, liquid crystals have giant optical nonlinearity due to the reorientational effect. Unfortunately, the response time in reorientational phenomena is large and its determination and reducing is very important issue. In this work the measurements of time of increasing the nonlinear reorientation in nematic layer are presented.
This paper presents results of tests performed on a fiber optic system of liquid crystalline transducer for hydrostatic pressure monitoring based on properties of colorimetry. The system employs pressure-induced deformations occurring in liquid crystalline (LC) cells configured in a homogeneous Frederiks geometry. The sensor is compared of a round LC cell placed inside a specially designed pressure chamber. As a light source we used a typical diode operating at red wavelength and modulated using standard techniques. The pressure transducer was connected to a computer with a specially designed interface built on the bas of advanced ADAM modules. Results indicate that the system offers high response to pressure with reduced temperature sensitivity and, depending on the LC cell used, can be adjusted for monitoring of low hydrostatic pressures up to 6 MPa. These studies have demonstrated the feasibility of fiber optic liquid crystal colorimeter for hydrostatic pressure sensing specially dedicated to pipe- lines, mining instrumentation, and process-control technologies.
We present a nonclassical method, with experimental verification, of the measurement of the elastic constants of nematic liquid crystal by applying the nonlinear optical effect. In the experimental set-up the optical fiber coupled with the semiconductor laser is used.
An original idea of hydrostatic pressure monitoring is presented. The paper reports latest result of liquid crystal-based fiber optic devices for hydrostatic pressure sensing in both low pressure and high pressure regions. In the low-pressure region, the fiber optic transducer based on properties of colorimetry employs pressure-induced deformations occurring in liquid crystalline cells, configured in a homogenous Frederiks geometry. However, in the high pressure region we propose another approach based on a liquid crystal-core anisotropic fiber acting as a sensing medium due to pressure-induced changes in its birefringence. These fibers unite the unique advantages of liquid crystals and quality of fiber technology that can be used for instant pressure monitoring.