A photonic crystal fiber (PCF) for sensing of sulfuric acid is designed and analyzed using Comsol Multiphysics. To analyze the sensor performance, 0%, 10%, 20%, 30%, 40% H₂SO₄ solution is placed into the fiber separately and then relative sensitivity, confinement loss, birefringence, effective area etc. are investigated for each solution over wavelength ranging from 0.8 to 1.8 µm. The sensor structure affords moderately high relative sensitivity and around 63.4% sensitivity is achieved for the highest concentration of H₂SO₄ at the wavelength 1.5 µm in x polarization direction. This PCF model also shows zero confinement loss for all solutions of H₂SO₄ over wavelength ranging from 1 to 1.35 µm and later on approximately 1.422 × 10⁻¹⁷ dB/km confinement loss is found for the highest concentration of H₂SO₄ at 1.5 µm wavelength. Besides, higher birefringence is attained when the concentration of sulfuric acid is lower and it is achieved 7.5 × 10⁻⁴ at 1.5 µm wavelength. Moreover, higher sensing area is achieved at high concentration of sulfuric acid.

Introduction: Ongoing amelioration of semiconductor nano-crystal in chemical sensing applications has led the Photonic Crystal Fiber (PCF) as the most appropriate candidate for chemical sensing. A PCF based sensor model has been proposed in this paper. Objective: The aim of this model is to detect formalin at a high level of sensitivity. Method: This sensor model has been designed and simulated in COMSOL MULTIPHYSICS to analyze the sensing performance based on the optical parameters such as relative sensitivity, confinement loss, and effective material loss. Formalin solution is placed into the core and then the simulation is performed in THz regime ranging from 1 to 2 THz to carry out the optical properties. Simulation data collected from COMSOL are used in Matlab to carry out the graphical representation of the optical parameters. Results: Simulation results demonstrate that the sensor model inherits high relative sensitivity of approximately 77.71 % at 1.8 THz. In addition to that, the proposed sensor exhibits zero confinement loss above 1.3 THz and very low effective material loss in the THz regime for the optimum model. Conclusion: All the optical parameters maintain standard and desirable values in the THz regime. Besides, the flexible fabrication of the proposed model is feasible using existing fabrication methods. Simulation results validate the high performance of this proposed model in formalin detection.

In this paper, a dual-core liquid filled photonic crystal fiber coupler (PCFC) with rectangular (RPCFC) and hexagonal (HPCFC) geometry is presented from the 1200 to 1800 nm wavelength range. In the proposed design, super flint (SF10) glass is used as the background material and water, chloroform, and benzene are infiltrated in the dual-core, independently. The properties of the guided modes are studied by the finite difference time domain (FDTD) method with a perfectly matched layer (PML) boundary condition. Results reveal very small confinement loss with a low coupling length and birefringence for the wide wavelength range. At the 1.55 μm wavelength, RPCFC shows 0.000318, 0.000358, and 0.000379 m coupling lengths for the water, chloroform, and benzene filled dual-core, respectively. Additionally, the confinement loss of 1.57×10⁻⁷, 1.22×10⁻⁷, and 1.05×10⁻⁷ db/km is achieved through RPCFC. Moreover, both the PCFCs present a small polarization variation. Therefore, the proposed PCFC models can be used in optical communication systems, and polarization-independent and high temperature-sensitive applications areas.

Introduction: This paper demonstrates the design of a sensor model for the detection of Sodium Chloride (NaCl) in an effective and efficient manner. Photonic Crystal Fiber (PCF) has been used to design this sensor model. Objective: Using Comsol Multiphysics software, the sensor model has been implemented and simulated to carry out an in-depth analysis of the sensing performance of the proposed model. Method: The confinement loss, effective material loss, effective area, birefringence, and relative sensitivity were analyzed to estimate the sensing efficiency of this model. The sensor performance has been analyzed for five different concentrations of NaCl. Results: From the analysis, it is found that for all the analytes, confinement loss maintains a moderate value for the frequency band ranging from 0.9 to 1.2 THz. However, it approaches absolute zero immediately after 1.2 THz. The sensor model results in a high effective area, which is highly desirable for every PCF. It shows 3.78 × 105, 3.77 × 105, 3.76 × 105, 3.75 × 105, and 3.743 × 105 μm2 effective areas for 0%, 20%, 40%, 60% and 80% NaCl, respectively, at 1.4 THz. The effective material loss for this model is about 3.7×10-3, 3.63×10-3, 3.68×10-3, 3.672×10-3 and 3.652×10-3 cm-1 for 80%, 60%, 40%, 20% and 0% NaCl, respectively, at 1.4 THz. Birefringence is also high for the proposed model. The values of birefringence are approximately 0.002, 0.0018, 0.0017, 0.0016 and 0.0015 at 1.4 THz for 0%, 20%, 40%, 60% and 80% NaCl, respectively. In addition to the above positive outcomes, the sensor model exhibits high sensitivity for both x and y polarization. The peak sensitivity of this sensor is 91.5%, 91.42%, 91.34%, 91.25% and 91.10% in x polarization direction whereas the peak sensitivity is 91.70%, 91.60%, 91.49%, 91.40% and 91.25% in y polarization direction for 80%, 60%, 40%, 20% and 0% NaCl, respectively, at 1.8 THz. The value of sensitivity is above 90% at 1.4 THz for all the five concentrations of NaCl. Conclusion: The analyzed optical properties signify the higher efficiency and effectiveness of the sensor model in the detection of NaCl.