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A magnetic field sensor based on a Sagnac interferometer using a magnetic fluid-filled birefringent photonic crystal fiber (MF-BPCF) was proposed and studied by finite element method. Two large air holes in the birefringent photonic crystal fiber were designed to fill with magnetic fluid. The MF-BPCF in the proposed Sagnac interferometer acted as the sensing head. As magnetic field perpendicular to the MF-BPCF, magnetic fluid was anisotropic. The characteristics of the output spectrum of the Sagnac interferometer was simulated. The results showed that when the phase difference $\phi$ satisfied integer multiples of $2\pi$ , several dip wavelengths appeared. Not only the intensity but also the direction of the magnetic field was measured. The measuring sensitivity could be further promoted by making the dip wavelength approach $\lambda _{B_g=0}$. [ABSTRACT FROM AUTHOR]

With the homemade solid-core silica-based photonic crystal fiber (PCF), we observe the generation of soliton and four-wave mixing (FWM) when the femtosecond pulse is pumped at 0.822 \mu\m , belonging to the normal-dispersion regime. It is generally acknowledged that FWM is unrelated to third-order dispersion, whereas we use the fourth-order Runge–Kutta method to simulate the PCF properties by taking into account the third-order dispersion or not; the result we got is different from the conventional one. The numerical simulations are greatly consistent with the experiment results, and the FWM is dominated by negative fourth-order and negative sixth-order dispersion in the experiment. The main dynamic process is explained as the soliton, and the FWM generation can be induced by third-order dispersion. We indicate that low Raman threshold has played a very active role in this process, and we propose a conception of stimulated FWM effect in this paper. [ABSTRACT FROM PUBLISHER]

A circular ultra-short A s 2 S 3 filled double-core photonic crystal fiber polarization beam splitter is proposed. The finite element method is used to study the performance of the designed photonic crystal fiber polarization beam splitter. By filling high refractive index A s 2 S 3 into the central air hole, the coupling performance of the double-core PCF is improved. By optimizing geometric parameters, the splitting length of the circular beam splitter can be as short as 72.43 μ m, and the extinction ratio can reach −151.42 dB. The high extinction ratio makes the circular polarization beam splitter have a good beam splitting function. The designed circular double-core photonic crystal fiber has the same cladding pore diameter, which is easier to prepare than other photonic crystal fibers with complex pore structure. Due to the advantages of high extinction ratio, extremely short beam splitting function and simple structure, the designed polarization beam splitter will be widely used in all-optical networks and optical device preparation. [ABSTRACT FROM AUTHOR]

This paper proposes a highly sensitive surface plasmon resonance (SPR) refractive index sensor based on the photonic crystal fiber (PCF). The optical properties of the PCF are investigated by modulating the refractive index of a liquid analyte. The finite element method (FEM) is used to calculate and analyze the PCF structure. After optimization, the fiber can achieve high linearity of 0.9931 and an average refractive index sensitivity of up to 14,771.4 nm/RIU over a refractive index range from 1.47 to 1.52, with the maximum wavelength sensitivity of 18,000.5 nm/RIU. The proposed structure can be used in various sensing applications, including biological monitoring, environmental monitoring, and chemical production with the modification and analysis of the proposed structure. [ABSTRACT FROM AUTHOR]

This paper proposes a Photonic Crystal Fiber (PCF) refractive index sensor model based on the surface plasmon resonance effect. The proposed PCF model also uses the full vector finite element method to transfer the structure under the anisotropic Perfect Matching Layer (PML) boundary condition. Numerical calculations were carried out on the sensor characteristics. The calculation results show that the elliptical air hole on the left side of the PCF core is coated with a gold-nano film which serves as a Surface Plasmon Resonance (SPR) sensing channel to detect the refractive index of liquid materials. Compared with other structures, the resonant peak generated by the excited SPR effect from the elliptical sensing channel has a high sensitivity to the change of the refractive index of the liquid to be measured. With the help of this attribute, it is relatively easy to adjust the sensitivity. The refractive index range of this structure is within 1.43–1.49 and the sensitivity is up to 12,719.97 nm·RIU−1. The linearity is good; R2 = 0.99927, which is very suitable for liquid sensing. [ABSTRACT FROM AUTHOR]

In this paper we propose a gold-plated photonic crystal fiber (PCF) refractive index sensor based on surface plasmon resonance (SPR), in which gold is coated on the external surface of PCF for easy fabrication and practical detection. The finite element method (FEM) is used for the performance analysis, and the numerical results show that the thickness of the gold film, the refractive index of the analyte, the radius of the air hole in the first layer, the second layer, and the central air hole can affect the sensing properties of the sensor. By optimizing the sensor structure, the maximum wavelength sensitivity can reach 11000 nm/RIU and the maximum amplitude sensitivity can reach 641 RIU−1. Due to its high sensitivity, the proposed sensor can be used for practical biological and chemical sensing. [ABSTRACT FROM AUTHOR]