In this work, we propose a new sensitive polarization optical security system. This system takes advantage of the unique and interesting properties of polarization holograms, which can encode polarized complex fields. The system is controlled by an interface, which has three defined parameters and a target image. These parameters are compared with the parameters obtained of the PH Fourier diffraction intensity pattern and recovered field. We present experimental results to probe the effectiveness of the system.
The interesting propagation properties of periodical gratings have been widely studied in the last decades. A special characteristic involving periodical structures is the self-imaging, in free propagation. Commonly the Talbot effect only consider the scalar nature of the fields, however the vectorial nature of the fields also plays an important role in free propagation. In this work, we study theoretically and experimentally the free propagation at fractional Talbot distances of inhomogeneous polarization periodical gratings, which are characterized by orthogonal polarization states. We found that the polarization states change in a peculiar way at different planes. We also generate some particular polarization gratings by means of a spatial light modulator and demonstrate that the theoretical and experimental results are in good agreement.
Dispersion is a quite important parameter in optical fiber systems, mainly in pulsed lasers where the temporal width of the pulses are affected by this factor. There are many interferometric arrangements to evaluate this parameter and generally, these systems vary the wavelength to obtain information about the refractive index dependency n(λ), which is contained in the interferogram phase. However, this makes the system quite slow and it requires tunable light sources with a narrow bandwidth. In this work we propose an alternative method to measure dispersion and we present the results of measurements of special optical fibers, such as microstructured, Er doped, Yb doped, and Er/Yb doped fibers, among others. The experimental arrangement consists of a Mach-Zehnder interferometer, where the fiber under test is located in one of its arms while the air is employed as the reference arm. In order to determine the n(λ) dependency, a wide spectrum light source in the wavelength range of interest was used together with an optical spectrum analyzer. The phase information was evaluated from the measured interferogram. The obtained dispersion values were in agreement with those reported by the fabricant and they were used to calibrate the system in order to obtain non reported values.
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