A novel ultra-high tunable photonic crystal fiber (PCF) polarization filter is proposed and analyzed using finite element method. The suggested design has a central hole infiltrated with a nematic liquid crystal (NLC) that offers high tunability with temperature and external electric field. Moreover, the PCF is selectively filled with metal wires into cladding air holes. Results show that the resonance losses and wavelengths are different in x and y polarized directions depending on the rotation angle φ of the NLC. The reported filter of compact device length 0.5 mm can achieve 600 dB / cm resonance losses at φ = 90° for x-polarized mode at communication wavelength of 1300 mm with low losses of 0.00751 dB / cm for y-polarized mode. However, resonance losses of 157.71 dB / cm at φ = 0° can be achieved for y-polarized mode at the same wavelength with low losses of 0.092 dB / cm for x-polarized mode.

An asymmetric dual-core photonic crystal fiber (ADC-PCF) wavelength-selective polarization splitter is reported and analyzed. The left core of the DC-PCF is surrounded by nematic liquid crystal infiltrated holes in order to control the wavelength at which coupling occurs between the dual cores of the proposed design. Moreover, the suggested structure can be tuned to split out the $x$- and $y$-polarized modes at the two telecommunication wavelengths $\lambda =1.3\mathrm{\mu m}$ and $\lambda =1.55\mathrm{\mu m}$. The geometrical parameters of the reported splitter are studied by the full vectorial finite difference method via the Lumerical software package to achieve high wavelength selectivity with device length of 5.678 mm at $\lambda =1.3\mathrm{\mu m}$. Further, the power coupling characteristics of the reported device are studied, which ensures that the ADC-PCF splitter has a very narrow bandwidth of approximately 3 nm around wavelengths of 1.3 μm and 1.55 μm. Therefore, the suggested design can be considered as a very good candidate to be used in the integrated photonic devices.

In this paper, highly efficient multi-functional biosensor based on surface plasmon resonance (SPR) is proposed and analyzed. The suggested sensor has a dual core PCF infiltrated with temperature dependent alcohol mixture. In addition, two gold nanorods are mounted vertically at the inner surface of the central PCF hole that is infiltrated with the studied analyte. Through the proposed biosensor, both analyte refractive index (RI) and temperature can be detected. The geometrical parameters of the reported structure are studied to maximize the sensitivity. Full vectorial finite element method (FVFEM) is utilized throughout the numerical analysis of the reported structures. The reported multi-functional biosensor achieves high temperature sensitivity of 21.05 nm/°c and very high refractive index sensitivity of 34600 nm/RIU. The achieved RI and temperature sensitivities are higher than the recent reported sensors in the same wavelength and temperature ranges.

Nowadays, the development of modern optical systems relies on optical device size minimization and operating power reduction. Optical modulator based on silicon on insulator (SOI) platform is a key element in different optical systems. Therefore, the optical modulator with compact size and low insertion loss could improve the optical system efficiency. In this work, a novel compact optical modulator based on hybrid plasmonic/silicon layers is introduced. The full vectorial finite element method (FV-FEM) is used to numerically analyze the proposed design. Vanadium dioxide (VO₂) is also utilized as a cap layer to control the modulation process. The insertion loss (IL) and extinction ratio (ER) of the suggested modulator are equal to 2.1 dB/µm and 28 dB/µm, respectively, at the operating wavelength 1.55 µm. Consequently, high figure-of-merit (FoM) =ER/IL = 13.5 is achieved with an optical bandwidth (ER > 3 dB) greater than 1 µm, which is large in comparison to pervious designs.