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Numerous techniques and technologies have been proposed for the detection and identification of hazardous chemicals that can harm the lungs and respiratory system as well as the central nervous system and kidneys when inhaled. Most practical techniques can be carried out by extraordinary professionals in well-equipped facilities. A reliable, simple, highly sensitive, and feasible sensing technique is still required. A potential sensor for these harmful chemicals is the photonic crystal fiber (PCF), which achieves several unique properties. A square-core PCF sensor is proposed in this work for the detection of detrimental gases (tetra-chloro silane, tetra-chloro methane, turpentine, and tin terra-chloride) in the THz region. The cladding region is divided into three rings, and each ring has rectangular and square air holes. Within the operating region, we have found a relatively high sensitivity of 96.185% along with 95.407% core power fraction, 0.2211 numerical aperture, and a low effective area of 154 470 μm2 at 1.9 THz frequency. Ignorable confinement loss of 3.071 × 10−14 cm−1 and effective material loss of 0.007 72 cm−1 have been also found. Additionally, the current manufacturing techniques guarantee the viability of the proposed PCF sensor's manufacture. These obtained results demonstrate that the proposed sensor can be effectively employed for applications involving hazardous chemical compounds, gases, and biosensing. [ABSTRACT FROM AUTHOR]

The significance of light absorption is highlighted in the development of photovoltaic applications. This study explores the absorption characteristics of a defective photonic crystal (PhC) in the GHz range. The PhC has the structure (SiO2/metamaterial)N/graphene/defect/graphene/(SiO2/metamaterial)N. The defect layer is considered as a SiO2 layer positioned between two graphene sheets. Transmittance, reflection, and absorbance are all investigated. The tunability of absorption characteristics is explored by varying the following parameters: the number of PhC periods, the chemical potential of graphene, the phenomenological scattering rate, and the thickness of the metamaterial layer. The results have shown that the number, frequency position, and intensity of the absorption peaks can be tuned through the change of the optical properties of graphene. The spectra are examined with and without graphene sheets, illustrating that the introduction of two graphene sheets can improve the absorption peaks. This innovative photonic device holds potential in the design of optical components such as filters, absorbers, and sensors in the GHz spectrum, utilizing graphene and metamaterial principles. [ABSTRACT FROM AUTHOR]

To ensure good water quality, microbiological contamination in water must be detected. This process is made easier and more distinctive using a photonic crystal fiber (PCF), which offers outstanding optical sensing capabilities. Herein, a PCF sensor model is proposed for detecting two types of waterborne bacteria, namely, Vibrio cholera and Escherichia coli bacteria. The core region of the proposed PCF sensor is made up of a single rectangle and the cladding region has 32 rectangular air holes that have the same height and width as the core rectangle. Zeonex is employed as the fiber material. Using Comsol 5.6 which is based on the finite‐element method, the model is numerically analyzed and structured. The simulation verifies the effectiveness of the proposed PCF to detect the analyte samples. Numerous performance indicators are calculated at an operating 2.8 THz. Simulation results show that the proposed PCF sensor is promising. Extremely high relative sensitivity (97.996%), lower effective area (6.3575 × 104 μm2), higher numerical aperture (0.23319), lower effective material loss (0.0034 cm−1), and lower confinement loss (0.1 × 10−14) are obtained which indicate an efficient PCF sensor. Additionally, the simplicity of the PCF design ensures the fabrication possibilities of the proposed sensor. [ABSTRACT FROM AUTHOR]

The tuning of a defect mode in a photonic crystal (PC) is of high significance for filter and sensor applications. We here investigate the tuning of the defect mode of a defective ternary PC with a semiconductor and high critical-temperature superconductor layers. A ternary photonic crystal with the heterostructure (semiconductor/superconductor/dielectric) is assumed. The transfer matrix method is employed to investigate the transmission of transverse electric waves. The refractive indices of the semiconductor and superconductor layers can be tuned by changing the operating temperature and the hydrostatic pressure. The defect mode and transmission properties can be controlled by using the hydrostatic pressure, operating temperature, frequency and thicknesses of the heterostructure layers. The analysis is performed in the frequency range of 20–65 THz. The proposed structure can be utilized as a biosensor and a narrowband transmission peaks filter. [ABSTRACT FROM AUTHOR]