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This paper presents the design and theoretical analysis of a photonic crystal fiber (PCF) based chemical sensor model. To evaluate the efficiency of this model, various optical parameters are analysed using finite element method based COMSOL Multiphysics Software. Different analytes namely methanol (1.317), water (1.330), ethanol (1.354) and benzene (1.366) have been considered for the sensing purpose in this study. The core region is infiltrated with different analytes separately. The model is simulated in THz regime (0.5–1.5 THz) to evaluate optical properties. The proposed structure design exhibits a high relative sensitivity of 96.85%, 97.32%, 97.99% and 98.33% for methanol, water, ethanol, and benzene, respectively at an operating frequency of 1.3 THz. The proposed model demonstrates exceptionally low confinement loss values which are 2.22 × 10–12 dB/m for methanol, 1.16 × 10–11 dB/m for water, 1.34 × 10–11 dB/m for ethanol and is 1.30 × 10–12 dB/m for benzene. Additionally, the effective material loss for the designed PCF also comes out to be very low for all the analytes, 0.0044 cm−1 for methanol, 0.0040 cm−1 water, 0.0034 cm−1 for ethanol and 0.0032 cm−1, for benzene. Furthermore, the PCF shows large effective mode area and numerical aperture (NA) within the mentioned range, at 1.3 THz. The NA values obtained at 1.3 THz are 0.32 for methanol, 0.40 for water, 0.32 for ethanol, and 0.32 for benzene. The obtained Effective mode Area (EMA) values are 1.46 × 105 μm2 for methanol, 1.45 × 105 μm2 for water, 1.44 × 105 μm2 for ethanol and 1.43 × 105 μm2, for benzene. Subsequently, the optimal profile provides birefringence values of 0.0009 for methanol, 0.0010 for water, and 0.0011 for both ethanol and benzene. The practical implementation of the proposed PCF structure is possible using subsisting modern fabrication techniques. Consequently, the proposed PCF design should be helpful in industrial areas for chemical research, food and biomedical sensing. [ABSTRACT FROM AUTHOR]

A unique PCF detector is suggested that contains octagonal cladding and hexagonal core which is used for kerosene adulteration detection. The sensor performance was numerically investigated between the frequencies of 1.0 and 2.8 THz. The central hole has been full with kerosene. The strut size is adjusted to investigate This research as well as the detector’s functionality be carried out at THz frequencies. At 2.2 THz, the photonic crystal fiber sensor has a relative sensitivity of roughly 94.25%, EML 0.01106, and a confinement loss of 1.77 × 10−13 of the order of 1014. This suggested detector can play a fine role in detecting kerosene admixture since it has high sensitivity and remarkable precision. This will be helpful for consumer to consume high-grade petroleum fuel without admixture of kerosene. Technologies related to extrude and 3D print might be utilized for the photonic crystal fiber detector. [ABSTRACT FROM AUTHOR]

A photonic crystal fiber (PCF)-based multi-analyte refractive index sensor is introduced in this study for the detection of four waterborne pathogens: Vibrio cholerae, Bacillus anthracis, Escherichia coli, and Enterococcus faecalis. The sensor comprises a tri-core structure with hexagonal rings encased in a silica substrate. Two selective holes are infused with water samples, enabling concurrent detection of two analytes. The sensor integrates liquid-silica mode coupling as its sensing mechanism. The couplings are precisely estimated and numerically evaluated using a finite-element method (FEM)-based simulation tool. The optimization of the sensor’s structural characteristics resulted in wavelength sensitivity of 6386 nm/RIU, 7104 nm/RIU, 8510 nm/RIU, and 3409 nm/RIU for sample pairs of V. cholerae–pure water, V. cholerae–V. cholerae, V. cholerae–B. anthracis, and E. coli–V. cholerae, respectively. Furthermore, the sensor exhibits the highest wavelength resolution of 1.59 × 10 - 5 RIU and figure of merit of 142 RIU - 1 and is also assessed for detection limit, detection accuracy, and signal-to-noise ratio. Featuring a straightforward design and remarkable sensing capabilities, the proposed sensor is anticipated to be exceptionally effective at detecting waterborne pathogens, with potential to excel in identifying chemicals, biomedical substances, and other diverse analytes. [ABSTRACT FROM AUTHOR]

This study introduces a distinctive entwined photonic crystal fiber (PCF) featuring two distinct and independent directed mode sections, collectively supporting a total of 112 orbital angular momentum (OAM) modes, comprising 76 + 36 modes. The confinement loss (CL) ranges approximately between 2.49701 × 1 0 - 11 and 9.13425 × 1 0 - 9 dB / m , while highest attained OAM purity is 99.31969 % and 98.99258 % at H E 2 , 1 mode, respectively, for both inner and outer rings. All the modes demonstrate ERIDs exceeding 1 0 - 4 , and minimum dispersion variation observed is - 856 ps / km - nm . Additionally, we achieved an outstanding isolation performance with the highest attained ISO reaching 294 dB at HE 9 , 1 mode and observed a substantial effective mode area of 9.15 μm2 and 25.8μm2, respectively, for inner and outer rings. This research leverages COMSOL Multiphysics' finite element method (FEM) and perfectly matched layer (PML) capabilities alongside MATLAB processing to calculate all key properties of the proposed fiber. Therefore, the suggested PCF demonstrates promising prospects for extended-range, high-capacity data transmission within optical communications and applications related to OAM sensing. [ABSTRACT FROM AUTHOR]

This study introduces a dual core photonic crystal fiber (DC-PCF) based biosensing approach for early detection of malaria in individuals by monitoring the variations in the red blood cells (RBCs). The proposed DC-PCF comprises four layers of a hexagonal lattice with circular air holes. In the proposed DC-PCF, we have used a central elliptical hole to infiltrate RBCs samples. The proposed study helps to detect various stages of malaria, such as infected RBCs, including the Ring stage, Trophozoite stage, and Schizont stage, by analyzing the changes in the peak wavelength. The proposed refractive index (RI) based sensor is designed to operate within an RI range of 1.33 to 1.41, enabling the detection of malaria. The numerical analysis indicate that our biosensor demonstrates significant sensitivity across different stages, such as 12,00000 nm/RIU for the ring stage, 11,15,263.15 nm/RIU for the trophozoite stage, and 11,13,793.10 nm/RIU for the schizont stage under x-polarization. Similarly, under y-polarization, the sensitivity is observed to be 10,50,000 nm/RIU for the ring stage, 10,54,736.84 nm/RIU for the trophozoite stage, and 10,32,758.62 nm/RIU for the schizont stage. The proposed DC-PCF-based biosensor is highly suitable for biological analysis and early malaria detection because it has a low detection limit and superior sensing performance. [ABSTRACT FROM AUTHOR]

In this paper, the 2D material MoO2 is innovatively chosen to replace traditional precious metals such as Au and Ag as the plasmonically excited material, and for the first time, it is combined with the extreme thermal optical material polydimethylsiloxane (PDMS). A D-type microstructured fiber is used as the optical information transmission medium and open sensing channel, and a surface plasmon resonance (SPR) effect based MOO2 coated D-type microstructured fiber temperature sensor is constructed. The simulation results show that the temperature detection range of the proposed optical fiber sensor is 30℃ ~ 80℃, and the sensing range of resonance wavelength is near the communication band of 1550 nm. The sensor is very sensitive to temperature variations, in particular the average wavelength sensitivity is up to 9.217 nm/°C in the x-polarized direction and 9.443 nm/°C in the y-polarized direction. This means that the sensor can accurately measure small changes in ambient temperature and respond quickly to ensure stable system operation. Therefore, MoO2 as a plasmonic sensing material and PDMS as a temperature sensing material have great potential for fiber sensing applications. [ABSTRACT FROM AUTHOR]

In this work, a single-mode endless photonic crystal fiber (PCF) is proposed and theoretically analysed using the empirical relationship method. The designed PCFs are composed of three uniform rings of air holes arranged in a circular shape. Three samples of fibers (PCFsPure, PCFsdoped1 and PCFsdoped2) with the same structure but are only different in the material of core have been investigated. The guiding properties of PCFs are studied in terms of effective refractive index, confinement loss and dispersion profile. The numerical results show that the PCFsdoped2 exhibits good properties such as high refractive index, low confinement loss and red shifting in the zero dispersion compared to other samples. A red shifting in the zero dispersion, achieved in this study, may be important to generate the soliton fission. Moreover, all the designed PCFs perform a negative dispersion at higher d/Λ, which are used to obtain the coherence supercontinuum generation spectrum. The designed PCFs in this study can be used in the transmission of optical signals using different types of materials in the core structure of PCFs. [ABSTRACT FROM AUTHOR]

This study introduces a temperature sensor based on solid-core photonic crystal fiber that exhibits insensitivity to polarization. The coupling condition between the core and defect modes is investigated by employing the finite element method. To enhance sensitivity, a thermo-sensitive liquid with a refractive index of 1.65 at 25 °C is injected into the second ring air holes, and a polydimethylsiloxane layer is applied around the filled holes. The impact of the polydimethylsiloxane layer and air hole sizes on the sensing performance is thoroughly analyzed. The proposed sensor's sensing property is evaluated by varying the temperature from 20 to 80 °C, resulting in an average sensitivity of − 3.166 nm/°C. The correlation coefficient is as high as 0.99992 and demonstrates the high linearity of the designed sensor. The full-width at half-maximum and the figure-of-merit are 11 nm and − 0.287/°C, respectively. Furthermore, a resolution of 0.03191 °C and an accuracy of 0.091 /nm show an excellent performance for the proposed device. The sensor's desirable features include high sensitivity, linearity, symmetrical structure, and equal sensitivity for both X and Y polarizations, making it suitable for practical applications. Furthermore, by adjusting some geometrical factors such as the lattice pitch, diameter of holes, number of rings, and thickness and concentration of materials, the sensor can be optimized for favorable operating conditions. [ABSTRACT FROM AUTHOR]

Photonic crystal fiber (PCF) has shown a promising application in various fields of modern optics due to its excellent transmission characteristics. However, conventional numerical solution methods have limitations such as high computational effort and low efficiency in designing PCF structures and characterizing pulse propagation in PCFs. With the advancement of artificial intelligence technology, various types of intelligent computing approaches, especially intelligent algorithm and machine learning algorithm (IML), provide new perspectives to solve the above difficulties. Therefore, an increasing number of researchers are committed to using IML to break through the limitations of conventional methods and accordingly open up a new interdisciplinary research direction. This paper begins with a brief overview of common optical properties and typical algorithms. Subsequently, it reviews specific areas where PCF and IML are combined, including the prediction and optimization of optical properties, the design of polarization devices, fiber lasers and amplifiers, as well as the control and prediction of Supercontinuum generation. Finally, this paper offers insights into the future developments and challenges in this emerging interdisciplinary field. [ABSTRACT FROM AUTHOR]

In our study, we conducted a thorough analysis of the spectral characteristics of a D-shaped surface plasmon resonance (SPR) photonic crystal fiber (PCF) refractive index sensor, incorporating a full width at half maximum (FWHM) analysis. We explored four distinct plasmonic materials—silver (Ag), gold (Au), Ga-doped zinc oxide (GZO), and an Ag-nanowire metamaterial—to understand their impact on sensor performance. Our investigation encompassed a comprehensive theoretical modeling and analysis, aiming to unravel the intricate relationship between material composition, sensor geometry, and spectral response. By scrutinizing the sensing properties offered by each material, we laid the groundwork for designing multiplasmonic resonance sensors. Our findings provide valuable insights into how different materials can be harnessed to tailor SPR sensing platforms for diverse applications and environmental conditions, fostering the development of advanced and adaptable detection systems. This research not only advances our understanding of the fundamental principles governing SPR sensor performance but also underscores the potential for leveraging varied plasmonic materials to engineer bespoke sensing solutions optimized for specific requirements and performance metrics. [ABSTRACT FROM AUTHOR]

The photonic aspects of semiconducting hexagon-shaped photonic crystal fiber including effective mode area, effective mode index, dispersion, and confinement loss, have already been investigated. The finite element method has been used to compute the maximum distribution of the studied photonic crystal fiber by COMSOL software. The linear modifications from both the effective mode index and an effective mode area have been investigated. Dispersion and confinement loss are examined in terms of air hole ring number and wavelength. For every wavelength, the effective-index model implies that the studied fiber can indeed be single mode. Even though its practical single-mode range inside the opacity aperture of silica appears large, it is eventually confined by a bend-loss edge at both brief & medium wavelengths. Moreover, the reported fiber offers minimal confinement loss of almost 10−8 dB/cm, birefringence 0.0012, and dispersion around 10−11 ps/km nm. [ABSTRACT FROM AUTHOR]

Abstract A novel helically twisted photonic crystal fiber (PCF) is designed and proposed for sensing toxic gases with refractive indices ranging from 1.00 to 1.08. The PCF consists of twelve hollow pipes arranged circularly around the hollow core to support THz radiation propagation. Low-loss polymer Topas is used as the background material of cladding. The fiber is twisted 360° over 50 cm to enhance anti-resonance in the THz region. The fundamental LP01 mode is analyzed using the finite-difference eigenmode (FDE) method. The sensor operates across four frequency bands (0.2 to 3.0 THz) with minimal transmission loss (~ 10⁻⁴ 1/cm). Key parameters such as refractive index sensitivity, relative sensitivity, resolution, and figure of merit (FOM) are evaluated. The average refractive index sensitivities are 1450, 2250, 3000, and 2550 for Bands 1 to 4, respectively, with 100% relative sensitivity across all bands. The sensor detects refractive index changes as small as 10⁻⁴. The FOM, defined as the inverse of the full width at half maximum, exceeds 30 1/RIU, reaching up to 250 1/RIU due to sharp resonance peaks. Compared to other THz sensors, this design offers enhanced performance in sensing gases like SOx, NOx, and CO, while maintaining a simple structure.

This paper presents the design of a high-efficiency spot size converter (SSC) for photonic crystal fiber (PCF) to silicon-based waveguides, utilizing composite optical waveguide structures. The SSC is composed of a series of waveguide cores, with one core progressively widening to enable all cores to collectively serve as a composite input port, while the broader core functions as the output port. Simulation results reveal that the proposed design efficiently facilitates mode and energy transfer between the waveguide and the PCF, achieving a coupling efficiency of up to 93.99% over a length of 66 μm. Additionally, the SSC exhibits polarization insensitivity, with the high circularity of the output beam enhancing vertical alignment tolerance, and maintaining excellent performance over a wide wavelength range. In sum, this SSC demonstrates excellent coupling efficiency and holds significant promise for applications in optical communication systems and optical integrated circuit systems. [ABSTRACT FROM AUTHOR]

The proposed miniaturized biosensor, the dual-channel multi-analyte single polarization (DCSP) photonic crystal fiber (PCF) sensor, offers real-time measuring and high sensitivity, making it a promising candidate for future sensing devices. It was structured using the stack-and-draw technique to show the sensor practical feasibility. The DCSP PCF sensor offers maximum wavelength and amplitude sensitivities of 11,000 nm/RIU and 807 RIU−1, respectively in both channels for the analyte refractive index (RI) of na = 1.33 to 1.41. This DCSP PCF sensor has a birefringence of 11.2 × 10 - 4 . The use of DCSP PCF sensors improves the sensitivity to wavelength in detecting multiple analytes in real time. These sensors are suitable for biosensing applications, especially when working with small sample sizes. Additionally, DCSP PCF sensors operate at a single polarization, resulting in lower confinement loss and better wavelength resolution, which enhances their performance. These findings suggest that DCSP PCF sensors have the potential to enhance future sensing technology and improve the detection of diseases and liquid substances. [ABSTRACT FROM AUTHOR]

This paper proposed a photonic crystal fiber (PCF) sensor to detect low water content in ethanol. An Ag-TiO 2 layer is used to achieve high sensitivity of this surface plasmon resonance (SPR)-based sensor. Moreover, TiO 2 layer reduces chemical instability of silver and enhances SPR effect. This paper carried out numerical analysis of sensor using finite element method (FEM). For evaluating effectiveness of a sensor to detect a target analyte, its confinement loss, sensitivity to changes in amplitude and wavelength can be measured by tuning some impactful parameters like airhole diameter, thickness of silver (Ag) and titanium dioxide (TiO 2 ). The maximum amplitude sensitivity for detecting ethanol is 963 R I U - 1 and maximum spectral sensitivity is 12,000 nm/RIU. The sensor can detect 100% pure ethanol with respect to pure water. The linearity of the sensors has also been evaluated between refractive index 1.32–1.36, and the regression coefficient ( R 2 ) for this sensor is 0.99961. The fabrication process of the proposed sensor has been discussed elaborately. This under consideration biosensor shows promising feature for organic and biological compound detection due to its stability and excellent sensitivity. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance (SPR) sensor composed of photonic crystal fibers (PCFs) is designed for refractive index (RI) sensing with a high figure of merit (FOM). The dual Au-MgF2 layer is covered on the double-side polished D-type PCF to stimulate SPR. Our numerical analysis reveals that the maximum wavelength sensitivity and amplitude sensitivity of the PCF-SPR sensor are 59,000 nm/RIU and 6076 RIU−1, respectively, in the RI range of 1.25 ~ 1.43. The maximum FOM is 2033 RIU−1 and the resolution is 1.69 × 10−6. The results provide guidance and insights into the design of PCF-SPR sensors with high FOM. [ABSTRACT FROM AUTHOR]

We presented numerical estimates of the degree of quantum entanglement based on Schmidt mode analysis for ultra-broadband biphotonic states generated in a photonic crystal fiber. We show that these states have a high degree of quantum entanglement even when the source is pumped broadband by femtosecond laser pulses. [ABSTRACT FROM AUTHOR]

This paper presents the results of a detailed theoretical study of the bending properties of all-glass leakage channel microstructured optical fibers (LC MOFs) with a polymer coating over a bending radius range from 4.8 cm to 10 cm. The dependencies of the effective refractive indices of the LC MOF modes on the bending radius have a number of crossings and anticrossings for different mode pairs. A detailed analysis showed that eight modes for each polarization have to be considered to correctly calculate the bending losses. These modes can be classified into relatively strong modes (three for each polarization) and relatively weak modes. The three strong modes have the most direct effect on the loss calculation. However, the relatively weaker modes also play a role through their coupling with the stronger modes, resulting in the appearance of local loss maxima in the loss dependencies for the strong modes. At a bending radius of 10 cm, the final leakage loss of the LC MOFs with a polymer coating is approximately four times lower than that of the LC MOFs without a coating. The significant reduction in losses paves the way for further optimization of the LC MOF geometric structure, leading to a reduction in the allowable bending radius. [ABSTRACT FROM AUTHOR]

Polarization filters based on surface plasmon resonance (SPR) have undergone rapid development in recent years. In this work, a dual D-type PCF polarization filter based on SPR is designed and analyzed. The filter improves the limiting loss of the core mode by gilding the semi-circular split ring and inlaying amethyst. The influence of the structural parameters of the filter on the filtering characteristics is analyzed by the finite element method. The results show that the core mode losses of the x and y polarized light are 32 dB/cm and 910.56 dB/cm at 1.55 μ m, respectively. For a fiber length of 1000 μ m, the crosstalk and bandwidth are 763.11 dB and 700 nm, respectively. In addition, the impact of manufacturing errors in the structural parameters on the filter performance is discussed. The filter has excellent filtering characteristics and large potential in optical communication and optical sensing. [ABSTRACT FROM AUTHOR]

A novel cyclic olefin copolymer (COC)-based terahertz (THz) polarization beam splitter (PBS) employing photonic crystal fiber (PCF) with cascade hexagonal porous two-core structure is proposed. The porous two-core is achieved by replacing the original two large air holes with three layers of small air holes. The mode coupling characteristics between the even and odd modes in the x- and y-polarization directions for the proposed THz PBS are explored using the time-domain finite difference (FDTD) method. The influence of PBS structural parameters on its coupling length is investigated. Numerical analysis results indicate that the bandwidths of 227.8 GHz (ranging from 1.8970 to 2.1248 THz) and 147 GHz (ranging from 1.928 to 2.075 THz) are acquired for the x- and y-polarization fundamental modes, respectively. The highest extinction ratios (ERs) are 114.5 dB and 72.3 dB, and the minimum insertion losses (ILs) are 0.0142 dB and 0.0369 dB for the x- and y-polarization fundamental modes, respectively. Moreover, the length of the proposed PBS is merely 11.655 mm. The proposed PBS will find potential applications in polarization-diverse THz systems, including broadband line-of-sight communication, real-time security checks, and high-resolution imaging. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrated a method of filling the air holes of a photonic crystal fiber (PCF), coated with gold film, with magnetic fluid (MF) to enhance the Surface Plasmon Resonance (SPR). The simulation results show that at the wavelength of 1260–1675 nm, the minimum loss coefficient of the y-polarization mode is 4.7 times that before filling with MF, and the x-polarization mode is 0.45 times greater. Then, based on this method, we designed a polarizing filter with a core diameter of 9 µm. The numerical simulation results indicate that it not only maintains the same core diameter as the single-mode fiber, but also has a larger bandwidth and a higher extinction ratio (ER). Additionally, we can optimize its ER at a specific wavelength by adjusting the magnetic field. [ABSTRACT FROM AUTHOR]

A high sensitivity photonic crystal fiber (PCF) magnetic field sensor based on Sagnac interferometer is proposed. All the air holes of the PCF are completely filled with the magnetic fluid (MF), which is a magnetic liquid material. The sensing performance of PCF is simulated and analyzed by using finite element method (FEM). It is found that the effects of wavelength λ, phase birefringence B(λ,H), and group birefringence Bg(λ,H) on the sensitivity are very significant. The two dip points in this spectrum show a red shift and a blue shift as the refractive index of the magnetic fluid increases, respectively. This magnetic field sensor obtains the average sensitivity of 889.5 pm/Oe (111,684.9 nm/RIU) and −994.3 pm/Oe (−124,839.5 nm/RIU) in the range from 90 to 240 Oe. [ABSTRACT FROM AUTHOR]

This paper presents a photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor designed to achieve precise malaria detection in blood samples. The sensor's innovative architecture incorporates carefully optimized layers of plasmonic materials, including gold and TiO2, to attain sensitivity and specificity. Extensive assessment of this sensor's performance has been carried out through rigorous finite element analysis using COMSOL Multiphysics v5.6. The sensor's configuration features a gold-coated PCF with a thin analyte layer, enabling the external detection of malaria parasites within blood samples. The air-hole configuration of the PCF sensor resembles the shape of a "barred spiral galaxy". It has undergone comprehensive testing across various stages of infected blood cells (ring, trophozoite, schizont), as well as normal red blood cells, each with their distinct refractive indices (RI). Through meticulous adjustments to the sensor's geometric parameters, remarkable wavelength sensitivity of 17,857.14 nm/RIU and amplitude sensitivity of 442.92 RIU−1 have been achieved for the ring phase, 10,210.53 nm/RIU and 392.72 RIU−1 for the trophozoite phase, and 8758.62 nm/RIU and 352.86 RIU−1 for the schizont phase. The numerical investigation also shows that the sensor possesses a low confinement loss of 50.25 dB/cm, 34.97 dB/cm, 28.74 dB/cm, and 25.47 dB/cm for normal RBC, ring phase RBC, trophozoite phase RBC, and schizont phase RBC, respectively. The results confirm the potential of the proposed sensor to detect malaria compared to existing methods. Hence, this sensor holds significant promise for advancing malaria detection and monitoring in blood samples, potentially leading to improved diagnostic and management strategies for this disease. [ABSTRACT FROM AUTHOR]

In this paper, we present a tetragonal cluster-based photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor with high wavelength sensitivity (WS). Indium tin oxide (ITO), as a dielectric material with adjustable photoelectric properties and low loss in the infrared range, is used in this sensor. The central rectangular air hole is used to construct an asymmetric structure which enables the sensor work in y and x polarization. We optimized the structural parameters of the sensor and the result shows that the sensor has high WS of 31,500 nm/RIU and 31,000 nm/RIU, wavelength resolution of 3.17 × 10−6 RIU and 3.23 × 10−6 RIU, maximum AS of 141.0 RIU−1 and 148 RIU−1, the refractive index (RI) detection range of 1.32–1.42 for y and x polarization, respectively. The sensor shows great potential in the detection of plasma, ethanol, and silicone oil. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance (SPR) biosensor based on dual-side polished photonic crystal fiber (PCF) has been presented in this paper. An external gold (Au) coating was used as a plasmonic material to detect changes in an analyte refractive index (RI). Sensor's structural parameters were optimized for better performance. The proposed sensor's simulation was conducted using the finite element method (FEM). Analytes within the RI range of 1.30 to 1.40 were used to develop a sensor. The numerical results are expected to have a wavelength sensitivity (WS) of 9400 nm/RIU and amplitude sensitivity (AS) of 27.27 RIU−1, respectively, and a spectral wavelength resolution of 1.063 × 10−5. Furthermore, it is expected to obtain maximum loss of 161,270 dB/m for a Y-polarization (Y-P) odd mode with an analyte RI = 1.37. We obtained an extinction ratio of − 321.54 dB for the polarization filter effect, which is considered to be good. This structure has the advantages of being easy to fabricate, affordable, and expected to show better sensitivity than many other sensors. It assumes to detect a wide range of analytes, making it suitable for organic chemical sensing, pharmaceutical inspection, and biosensor applications. [ABSTRACT FROM AUTHOR]

A wavelength-switchable polarization mode filter (PMF) based on a graphene-coated D-shaped photonic crystal fiber (DPCF) is proposed. Due to the different coupling properties between the two polarized core modes and surface plasmon polariton (SPP) modes, the PMF is designed for y-polarized mode filtering. In order to enhance the interaction between the graphene and fiber, gold is coated on top of graphene. Finite element method is applied to analyze the performance. Results show that the filtering wavelength can be modulated by adjusting the chemical potential (μc) of graphene. Especially, a single-wavelength PMF can be switched to a dual-wavelength or a three-wavelength filter by increasing the value of μc. The extinction ratio is higher than 25 dB with a small device length of 100 μm over the wavelength range of 1.0~1.4 μm. The wavelength-switchable PMF has a great potential in polarization modulation, WDM communication system, and multi-parameter sensing. [ABSTRACT FROM AUTHOR]

In this study, a simple air-silica microstructure based on circular-lattice geometry is designed and analyzed to achieve an ultra-large negative dispersion coefficient and high birefringence simultaneously for dispersion compensation. The fiber design has been analyzed numerically by utilizing finite difference mode convergence technique. The influences of varying various geometrical parameters on the dispersion as well as on the birefringence properties have been examined. Through a systematic analysis, the geometrical parameters of the design have been optimized for achieving the desired results. Finally, two photonic crystal fiber designs for narrowband and another design for broadband dispersion compensation have been proposed. The proposed narrowband designs exhibit high negative dispersion of −10,388 and −4,542 ps/nm/km, with birefringence values of 4 × 10−3 and 5.4 × 10−3 at a wavelength of 1.55 μm, respectively. The computed FWHM of the dispersion curves of these designed fibers are found to be 30 and 100 nm, respectively. For the broadband design, dispersion coefficient between −452 and −1,408 ps/nm/km has been achieved over the wide wavelength range of 1.4 to 1.7 μm. Additionally, the compensation ratio and relative dispersion slope of the proposed broadband design have been computed. It is observed that the design provides a negative dispersion coefficient of −932 ps/nm/km and a relative dispersion slope of 0.0036 nm−1 at 1.55 μm wavelength with a birefringence value of 1.23 × 10−2. [ABSTRACT FROM AUTHOR]

For high birefringence photonic crystal fibres (PCF) operating in terahertz (THz) regime, an outstanding model of slotted porous core with triangular lattice-based hexagonal shape cladding has been presented in this study. In this proposed THz-PCF, a five-layer circular air holes arranged in hexagon configuration have been placed in the cladding area, and five rectangular air holes have been positioned in core region for investigating the THz-PCF in polarization maintaining applications. The asymmetrical rectangular slots in core area creates difference between x and y polarized THz waves to offer high birefringence. The compact geometry of hexagonal structure in cladding offers more useful power confinement. The designed PCF offers high birefringence of 0.0866, low effective material loss of 0.0786 cm−1, core power fraction of 42.7%, less confinement loss of 0.02598 cm−1, low dispersion of 0.0963 ps/THz/cm and very less effective area of 0.03 µm2 in a broad frequency range of 0.1–2.3 THz, according to the Finite Element Method based simulation results in COMSOL Multiphysics software. These features enable the proposed PCF to be a better choice for numerous applications like polarization filtering, sensing, short distance communication, etc. in THz photonic integrated circuits. [ABSTRACT FROM AUTHOR]

A numerical investigation of the impact of fourth-order dispersion in the dynamics of Gaussian pulse propagation in photonic crystal fiber is presented. Considering the importance of waveguide dispersion in photonic crystal fiber, higher-order dispersion, especially fourth-order dispersion, is found to be crucial and significantly affects the dynamics. To study the evolution of various pulse parameters during propagation, we adopt the generalized projection operator method to derive the pulse parameter equation. It is observed that the fourth-order dispersion is found to be critical and, hence, remarkably influences the dynamics. A detailed discussion is presented to give further insight into the impact of Fourth order dispersion. Different ansatz-like methods are also considered alongside the Gaussian ansatz. [ABSTRACT FROM AUTHOR]