We demonstrate that one can cancel the bending-induced linear birefringence in single-mode fibers by inducing a controlled anisotropy in a direction orthogonal to the bending plane. In particular, the controlled anisotropy can be generated by application of a lateral compressive stress on the fiber. This effect can be applied for the construction of birefringence-free fiber coils in Faraday sensor heads (e.g., in current sensors) to improve their sensitivity.
We describe a simple method for visualization of phase objects. The phase object is placed between a printed two-dimensional periodic pattern and a CCD camera. The ray deflection that is due to the phase object distorts the image of the pattern. This image is subtracted from a reference image and then, by squaring and low-pass filtering, a measurement of the two-dimensional refractive-index changes is obtained. Because the optical system does not require special alignment or illumination, the method presented has potential application for detection of gas leaks in industrial environments.
The electro-optical effect of size polydispersity in polymer-dispersed liquid-crystal (PDLC) films is investigated. Liquid crystal (LC) droplets of different sizes require different electric field amplitudes for director reorientation, which will produce a mismatch of effective refractive indices. This, in turn, will produce an increase in interdroplet scattering (i.e., decrease in the direct transmitted light) within a specific range of electric field amplitudes. We propose a phenomenological “two-size” model describing this enhanced “pseudo-off-state” achieved under application of an electrical field and present validation experiments. Our approach may be used to get more insight into the transmittance behavior of PDLCs affecting the contrast ratio.
A synchronous polarimeter was set up for the measurement of small rotation angles of the polarization plane of light. The polarimeter is based on a polarizer-Faraday modulator-analyzer structure with a synchronous detection scheme, which produces a linear system response. The theoretical background is studied, and the system performance is investigated experimentally. We achieved an accuracy of the order of 10(-4) deg, or 5 mg/dl of glucose in a 1-cm light path.
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