A liquid-crystal-filled polymer photonic crystal fiber is designed and numerically analysised for terahertz wave guiding. Bandgap-guiding terahertz fiber is obtained by infiltrating the cladding air holes of index guiding Topas photonic crystal fiber with liquid crystal 5CB. Structural parameter dependence and thermal tunability of the photonic bandgaps, mode properties and confinement losses of the designed fiber are investigated by using the finite element method. The bandgaps are formed based on antiresonances of the individual liquid crystal inclusions, so the positions of bandgaps depend strongly on the cladding hole diameter and weakly on the lattice constant. Bandgaps and the positions of the confinement loss minimum or peaks of the transmission spectra shift toward lower frequency as temperature increased from 25 °C to 34 °C due to the positive dno/dT of 5CB. Average thermal tuning sensitivity of -30 GHz/°C is achieved for the designed fiber. At the central frequency of the transmission band, high power transmission coefficient and thus low splicing loss between the aligned liquid-crystal-filled polymer photonic crystal fiber and the unfilled section is obtained. Our results provide theoretical references for applications of liquid-crystal photonic crystal fiber in sensing and tunable fiber-optic devices in terahertz frequencies.
The accuracy of numerical reconstruction phase directly affect the result of the digital holographic detection. Because the microscope objective causes additional secondary phase factor, resulting in phase distortion of the reconstructed image. In order to find the phase distortion present in the reconstruction process and take the appropriate way to achieve automatic compensation of phase, digital holographic microscopy in phase compensation issues are studied. Least-squares curve fitting method and choose a background profile data approach is employed to produce the phase mask, and several iterations of correction of mask data by profile data. The theoretical analysis and experimental comparison of this method was validated. The results show that this method can quickly and accurately for better phase distortion correction, while providing new ideas for efficient extraction of real phase.