High birefringence with low confinement loss photonic crystal fiber (PCF) has significant advantages in the field of sensing, dispersion compensation devices, nonlinear applications, and polarization filter. In this report, two different models of PCFs are presented and compared. Both the models contain five air holes rings with combination of circular and elliptical air holes arrangement. Moreover, the elliptical shaped air holes polarization and the third ring air holes rotational angle are varied. To examine different guiding characteristics, finite element method (FEM) with perfectly matched layer (PML) absorbing boundary condition is applied from 1.2 to 1.8 μm wavelength range. High birefringence, low confinement loss, high nonlinearity, and moderate dispersion values are successfully achieved in both the PCFs models. Numeric analysis shows that model-1 gives higher birefringence (2.75 × 10^–2) and negative dispersion (–540.67 ps/(nm$km)) at 1.55 μm wavelength. However, model-2 gives more small confinement loss than model-1 at the same wavelength. In addition, the proposed design demonstrates the variation of rotation angle has great impact to enhance guiding properties especially the birefringence.

A square-core photonic crystal fiber (PhCF) has been presented for liquid (petrochemical) sensing application. The sensor performance has been studied numerically in the frequency range from 1.2 to 3.8 THz. The core hole is filled with pure petrol, kerosene, and diesel. Strut size is varied to explore the sensor’s performance and the analysis is performed in terahertz (THz) frequencies. The photonic crystal fiber sensor shows a relative sensitivity of around 97.0% and a confinement loss in the order of 10⁻¹⁴ at 3.7 THz. This photonic crystal fiber sensor can be fabricated using extrusion and 3D-printing technologies.

Solid core circular and octagonal photonic crystal fibers (CPCF and OPCF) are proposed for analyzing different guiding properties such as dispersion, effective mode area, nonlinearity, and confinement loss from 0.8 to 2.6 µm wavelength. The proposed structures use three different types of background materials: SF10, BK7, and silica. Moreover, the fill fraction is varied by changing the diameter of the air hole where the lattice pitch is unchanged. The proposed PCFs show a high negative dispersion with low confinement loss and small effective mode area. In the proposed design, the finite element method with a perfectly matched layer absorbing boundary condition is used. At 1.8 µm wavelength with 0.6 fill fraction, the maximum negative dispersion of − 922.5 p s / ( n m . k m ) is observed for CPCF when the background material is SF10. In addition, at this particular wavelength, the confinement loss is observed to be very small. Moreover, − 560.12 p s / ( n m . k m ) dispersion is found for the similar condition at 1.55 µm wavelength. On the other hand, using BK7 as the background material, − 706.77 p s / ( n m . k m ) dispersion is found at 1.55 µm wavelength for CPCF. Results also imply that CPCF shows better performance than OPCF for a wide wavelength range. Furthermore, at 1.55 µm wavelength, silica-based glass exhibits maximum dispersion, whereas increasing wavelength flint type glass shows the similar result. Analyzing different guiding properties of PCFs has significant impact on broadband dispersion compensation applications, especially using SF10.