Optical lattices have several applications including super-resolution imaging, lithography, and light-tweezers. Compared with the conventional multibeam interference method, optical lattices in a tightly focused light fields are presented by cylindrical vector polarization illumination and multisector amplitude modulation. The polarization and phase difference of the illumination beam, including the size and relative position of the sectors, were analyzed using the vector diffraction theory. The obtained results indicate that the primitive cell shape of optical lattices can be controlled by the polarization direction of the illumination beam when the relative positions of sectors in the amplitude modulation mask are set. In addition, the period and primitive cell shape of optical lattices with hyper or complex constructions can be controlled by the relative positions of sectors, while the optical lattice zone primarily depends on the sector size. By combining polarization and amplitude modulation in a high numerical aperture optical system, these engineered optical lattices are potentially beneficial in expanding their applications.
A total internal reflection photonic crystal fiber (PCF) based on hexagonal core is proposed for gas sensing in a specific wavelength range. The higher sensitivity and lower confinement loss were realized by the structure of the proposed PCF consists of two layers with circular holes rotated hexagonally around a core region and six slotted air-hole in the cladding based on numerical analysis. The simulation results show that the enhancement of the relative sensitivity has been done by enhancing the diameter of the hexagonal shape air-hole cladding (d1) and the hexagonal arranged holes around the central solid core (d0) in this design. Also, the confinement loss has been reduced by enhancing the ratio of length to width of slotted holes (l/w) and decreasing the cladding air-hole diameters (d1). As the refractive index increases, the wavelength shifts toward the long wavelength. And in a certain temperature range, the transmission characteristics of the device does not change with the temperature. The results are helpful for designing high performance PCF for gas sensing applications.
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