This article presents the photonic crystal fiber (PCF) based surface plasmon resonance (SPR) biosensor for early detection of malaria disease in humans by measurement of the variation of red blood cells (RBCs). In the proposed PCF, two layers of air holes are arranged in a hexagonal lattice structure and a thin film of gold-coating is used over PCF for the occurrence of SPR phenomena. It occurs when surface plasmon polariton (SPP)-mode coupled with the core-mode during phase-matching conditions. Malaria infected RBCs samples are filled into the PCF, which have own refractive index (RI) that shift the SPR resonance wavelength during confinement loss measurement. The resonance wavelength of malaria-infected RBCs samples is different from their normal RBCs samples due to the difference in RI of infected and normal RBCs samples. The proposed work is helpful in the detection of different stages of malaria-infected RBCs such as ring phase, trophozoite phase and Schizont phase by measuring the shift in resonance wavelength. The calculated wavelength sensitivities of the proposed sensor for the ring phase, trophozoite phase and Schizont phase RBCs are 13714.29 nm/RIU, 9789.47 nm/RIU, and 8068.97 nm/RIU, respectively in x-polarized direction and 14285.71 nm/RIU, 10000 nm/RIU, and 8206.9 nm/RIU, respectively in y-polarized direction with the maximum detection limit of 0.029. The proposed PCF-based SPR biosensor is suitable for the early diagnosis of malaria disease due to its enhanced sensing performance (low detection limit and high sensitivity).

The promising properties of photonic crystal fibers (PCFs) have sparked the interest of a number of research organizations. Due to the PCF’s air holes, liquid or gas samples can be inserted into them. This permits a well-controlled interaction between confined light and sensing samples, enabling the development of novel sensing applications. That was never conceivable with conventional optical fiber. PCF applications in sensing fields can be divided into physical sensors and biochemical sensors based on the parameter being measured. Physical sensors measure pressure, temperature, refractive index (RI), curvature, vibration, torsion, electric field, and displacement, among other physical characteristics. Biochemical sensors can detect chemical and biological (such as antibody, cell, bacteria, enzyme, virus, nucleic acid, etc.) substances. The measurement of the chemical RI is a crucial component of biochemical sensors. Due to their close relationship with biosensors, chemical sensors are commonly referred to as biochemical sensors. This paper covers the detecting capabilities of SPR-based PCF biochemical and physical sensors in addition to a variety of ways to enhance their sensing capacities.

This paper proposes a photonic crystal fiber (PCF) based plasmonic biosensor for the detection of various blood compositions like red blood cells (RBCs), hemoglobin (HB), white blood cells (WBCs), plasma, and water. The finite element method (FEM) has been used to simulate and quantitatively evaluate this biosensor. The gold and titanium dioxide coated PCF operates on the surface plasmon resonance (SPR) theory, where the gold layer acts as a plasmonic material, and the titanium dioxide layer improves adhesion between the gold layer and the PCF surface. SPR occurs at the interface between gold and the sensing channel, when the core propagation mode is coupled with the surface plasmon polariton (SPP) mode in the vicinity of the phase-matching point. Due to the occurrence of SPR, the loss peak is noticed in the core propagation mode, and this loss peak is extremely sensitive to the various blood compositions that each have their unique refractive index (RI) poured into the sensing channel of the PCF. The proposed biosensor has maximum wavelength sensitivity of 12400 nm/RIU. However, the maximum amplitude sensitivity is −574.3 RIU ⁻¹ . Furthermore, with the maximum detection limit of 0.02, the refractive index resolution varies from $8.06\times {10}^{-6} {\mathrm {RIU}}$ to $5.0\times {10}^{-5} {\mathrm {RIU}}$ . As a result, it is safe to say that this biosensor will work admirably in terms of detecting blood compositions. Thus, the proposed biosensor will explore the broad realms of medical diagnostics.

A surface plasmon resonance (SPR) refractometric sensor based on gold (Au) and titanium dioxide (TiO ₂ ) coated Photonic Crystal Fiber (PCF) is presented for the quick detection of various types of cancerous cells. The cancerous cells and their corresponding normal cells are both considered to be liquid cells each with their unique refractive index (RI). Normally these cells are found in liquid form in the suitable media (food) required to live the cancerous/normal cell lines. Also in our detection case, liquid samples are easy to pump into the sensing channel of the proposed PCF by employing either pressure or capillary forces.The proposed PCF sensor works on the SPR principle, with the Au coating serving as the plasmonic material. This sensor is investigated using the COMSOL Multiphysics software computational tool that is based on the full-vector finite element method (FEM). A TiO ₂ coating has been applied to enhance adhesion between the Au layer and the PCF surface. Above the Au coating, cancerous cells samples are filled into the PCF. When the core mode of the PCF is coupled with the surface plasmon polariton (SPP) mode under the specific resonance circumstances, SPR will occur on the interface of the gold-sample cell, and in the core mode, the loss peak is observed at the resonance wavelength. Cancerous cells samples have a distinct loss peak than normal cells samples therefore the cancerous cells can be diagnosed by measuring the shift in resonance wavelength corresponding to the loss peak of cancerous and their normal cells samples. The proposed sensor may identify various cancerous cells such as MDAMB-231, MCF-7, PC12, HeLa, and Jurkat for the diagnosis of breast cancer type-1, breast cancer type-2, adrenal glands, cervical, and blood cancer respectively. The computed wavelengths sensitivities of the proposed PCF are 9428.57 nm/RIU, 10714.28 nm/RIU, 7571.43 nm/RIU, 5500 nm/RIU, and 6000 nm/RIU for the MDAMB-231, MCF-7, PC12, HeLa, and Jurkat cancerous cells, respectively. However, for various cancerous cells, the maximum amplitude sensitivity varies from -1387 RIU ^-1 to -1599 RIU ^-1 . Moreover, the sensor resolution ranges between 0.93×10 ^-5 RIU and 1.82×10 ^-5 RIU with a 0.024 maximum detection limit. Because of its improved sensing capability, the presented SPR refractometric sensor is appropriate for the early detection of cancerous cells.

This paper describes a gas detection sensor that is based on a microstructured-core photonic crystal fiber (PCF). The finite element method (FEM) is used to analyze the quantitative dependence of guiding properties on geometrical parameters along wavelength. The result shows that the structure provides high relativity sensitivity with minimal confinement loss for detecting various gases such as methane (CH ₄ ) and hydrogen fluoride (HF) because the proposed PCF introduces microstructured-core. According to the results of this simulation, an absorptive line of CH ₄ /HF gases could have a maximum relative sensitivity of about 44.47% at wavelength of $1.33 ~\mu \text{m}$ with the optimal design of the PCF. The proposed sensor has a confinement loss of around ${1.83\times 10}^{-8}$ dB/m, that is very low and suitable for use as a gas sensor. Furthermore, numerical aperture (NA), V-parameter, Marcuse spot size (MSS), and beam divergence (BD) are extensively investigated in the wavelength range of 1.3 to $2.2 ~\mu \text{m}$ . These findings should aid in the development of a high-efficiency PCF for gas sensing and monitoring air pollution.