SACM - United States of America
Permanent URI for this collectionhttps://drepo.sdl.edu.sa/handle/20.500.14154/9668
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Item Restricted PHASE RETRIEVAL AND 3D TOPOGRAPHY USING TRANSPORT OF INTENSITY(Saudi Digital Library, 2023-12-26) Alanazi, Nouf; Banerjee, Partha PTransport of intensity is a non-interferometric technique to obtain the phase of an object by recording optical intensities at different incremental propagation distances around the image plane. The transport of intensity equation (TIE) is also a convenient way to obtain unwrapped phases directly without the need of phase unwrapping techniques. The accuracy of TIE can be improved by incorporating the associated transport of phase equation (TPE). However, TIE (and TPE) suffers from the disadvantage in that image intensities must be recorded at multiple longitudinal distances around the image plane without any transverse misalignment. To avoid this issue, we have proposed a modified TIE with TPE (TIE+TPE) in this research utilizing electrically controllable optical path lengths through bias voltages across liquid crystals (LCs). The most significant advantage of using TIE+TPE with LC is that no physical movement of the detector array is needed to change the optical path lengths around the image plane, as required for the conventional TIE. Additionally, TIE+TPE with LC provides a more accurate evaluation of the phase. Also, this research investigates the combination of digital holography (DH) and TIE+TPE with LC to retrieve the image phase directly without any phase unwrapping. In both cases of phase retrieval, either using conventional imaging or holographic imaging, numericalexamples and simple experimental verifications are provided. In experiments, the 3D topology is recovered from the imaged phase. Finally, we propose a single-shot (single wavelength) alternative to 3D optical imaging that combines DH with TIE and DH with TIE and TPE to conveniently retrieve unwrapped phase and hence the 3D topography of partially bloody fingermarks deposited on substrates and coated with columnar thin films encapsulated by columnar thin films (CTFs).11 0Item Restricted DIELECTRIC AND ELECTRO-OPTICAL EFFECTS IN NEMATIC LIQUID CRYSTALS(Saudi Digital Library, 2023-08-02) Almatani, Bdoor; Gleeson, JamesThe present work studied the physical properties of a nematic LC material compound RT11165. The recently discovered ferroelectric nematic phase that carries a non-zero dipole moment exhibits in this material. Experimentally we used the Fréedericksz transition method in the nematic phase by measuring the light intensity through a planar nematic layer as a function of the amplitude and frequency of an applied voltage. The threshold voltage shows dependence on the frequency. In addition, the dielectric anisotropy and the splay elastic constant K11 are measured. The dielectric anisotropy indicates critical behavior at high frequencies relatively low as cooling toward the NF phase, while at low frequencies, it shows strong positive dielectric permittivity. Also, the dielectric spectroscopy shows two molecular relaxation modes detected at low frequency and temperature in the perpendicular component of the dielectric permittivity, and the strength of the relaxation frequency was found to be decreased. In contrast, it increases rapidly and smoothly in the parallel component.13 0