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In this work, gold nanoparticles (NPs) have been synthesized using second harmonic generation ND-YAG laser ablation in ethanol employing 532 nm and 1.064 nm wavelengths. Field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) spectroscopy, and UV–Vis absorption were employed to examine the structural, chemical, and optical properties of Au NPs. XRD results showed that all synthesized Au nanoparticles are crystalline in nature. The optical band gap upon ablation using the higher wavelength (1064 nm) was about 4.02 eV. The value of the optical band gap increases to reach a value of 4.22 eV at the shorter wavelength (532 nm). The FESEM results reveal the formation of smaller nanorod size at second harmonic generation (SHG) wavelength was found to be about 30 nm at wavelength 532 nm and 44 nm at 1064 nm. After that, finite element analysis is used to simulate the photonic crystal fiber (PCF) as biosensors, depending on the surface plasmon resonance (SPR) phenomenon using the COMSOL multiphasic program. The hollow core photonic crystal fiber (HC-PCF) HC-800 was thus overfilled with water. The confinement loss (CL) of the fundamental mode for the proposed PCF with and without the gold nanoparticles was calculated; we observe without gold NPs the CL at the water and colon tissue about 1.08E + 03 and 5.46E + 02 dB/m, while at use the deposited PCF with gold NPs, the results ensured the decrease more than in the confinement loss at the water and colon tissue about 1.01E + 03 and 3.16E + 02 dB/m with a clear shift toward higher wavelengths, also when calculating the sensitivity, to increase HC-PCF biosensor performance by using wavelength interrogation and amplitude measurements; it found the bio-liquid (colon tissue) has the best electric field using the gold nanowire (NW) layer in the biosensor equal to 68.8 V/m by comparison when without using the gold NW layer which leads to high sensitivity. [ABSTRACT FROM AUTHOR]

A graded-index (GI)-type photonic crystal fiber (PCF) that has an α-power effective refractive index profile operates as a multimode optical fiber and can be applied to a collimator for single-mode PCFs. The α-power effective index distribution is realized by an α-power air hole diameter distribution with uniform air hole pitch. However, a pressure controlling in fiber drawing is difficult due to the difference of air hole diameters in fiber cross section. In this paper, we propose a GI-PCF with uniform air hole diameter while the air hole pitch varies in radial direction. Light propagation characteristics in the Gaussian beam excited GI-PCF with uniform air hole diameter were theoretically studied. The period and amplitude of mode field diameter variation along the propagation direction for the innermost air hole pitch, air hole diameter, and radial distribution profile of the pitch were clarified. The collimator application of GI-PCF with uniform air hole diameter for a conventional single-mode PCF was investigated. The suitable GI-PCF structure to obtain high optical coupling efficiency and good tolerance for GI-PCF length error was clarified. Wavelength characteristics of the GI-PCF collimator were also studied. It was clarified that the appropriate GI-PCF length was longer for shorter operating wavelength in collimator application. [ABSTRACT FROM AUTHOR]

This article describes a photonic crystal fiber (PCF) with two cores as refractive index sensor that was built using COMSOL Multiphysics software by considering elliptical shaped air holes within the cladding. The two cores of the PCF are formed by an elliptical air hole at center, which represents two independent waveguides. The approach is intrinsically suited to investigate the sensor's performance, a full-vector Finite Element Method technique is employed. According to mathematical evidence, the proposed PCF based sensor has maximum sensitivities 9000 nm/RIU and 10,000 nm/RIU for x-polarized and y-polarized respectively. The sensing range of analyte is 1.35–1.39. The proposed sensor that has excellent sensitivity reveals an unmatched capacity for detecting chemicals, agents that cause cancer, biomolecules, and other analytes. [ABSTRACT FROM AUTHOR]

The gases which are generated in the industrial areas are very harm. Knowingly or unknowing the people who work near this hazardous area are affected lot and now it is the right time to detect these harmful gases in an efficient manner. In order to sense these hazardous gases a type of sensor that should sense these gases in an efficient manner, one such sensor is Photonic Crystal Fiber (PCF). The different gases such as SO3, Sicl4, CCl4, C10H16, Sncl4 are analyzed with the same Vertical PCF (V-PCF) and Horizontal PCF (H-PCF) gas sensor which was designed earlier for the detection of SO2 gas in an efficient manner. By maintaining the same design parameters different gases are sensed and compared with the SO2 gas outputs for the wavelength range of 0.8 μm to 1 μm. A sensitivity of 65.86% and 71.80% at 1 μm for C10H16, SnCl4, and other gases may be detected with the optimized V-PCF and H-PCF gas sensor. These gases are harmful and it will cause serious issues to the human beings. The different parameters such as sensitivity, effective mode area and attenuation are analyzed for different gases. [ABSTRACT FROM AUTHOR]

In this paper, we propose a hexagonal photonic crystal fiber (PCF) suitable for broadened mid-infrared supercontinuum generation. The designed PCF has five air-hole rings with three different air holes, arranged in a triangle pattern. The central air hole is filled with G e 10 A s 22 S e 68 and the inner wall of the air hole is coated with A s 2 S 3 . In the mid-infrared wavelength range of 3400 nm to 4500 nm, the supercontinuum bandwidth increases with the increase of the pump wavelength, peak power, and pulse width. When the pump light source with a peak power of 5 kW and the input pulse width is 200 fs, a 10 mm fiber can produce an extremely wide supercontinuum spectrum spanning 6000 nm. In addition, optical parameters including dispersion, confinement loss, effective mode area, and nonlinear coefficients are numerically investigated by the finite element method. The results show that at a wavelength of 4000 nm, the second order dispersion of the fiber is 8.81 × 10 - 27 s 2 m - 1 and the nonlinear coefficient is 972.5 W - 1 km - 1 . The designed photonic crystal fiber is stable, dispersion flat, and can meet the application requirements of obtaining broad supercontinuum spectrum. [ABSTRACT FROM AUTHOR]

This analysis represents a circular shape based cladding with two elliptical shape cores in photonic crystal fiber (PCF) for the terahertz (THz) range. Here, we present a single-mode photonic crystal fiber (SM-PCF) with five layers of circular shape of air holes (CAH) structure along with two layers of elliptical shape of air holes (EAH) core configuration in the center to decrease the different types of losses. For broad-band communications, our proposed SM-PCF is highly useful due to the obtaining of ultra-low effective material loss (UML) in the terahertz regime. Perfectly matched layers (PMLs) and finite element method (FEM) established on COMSOL Multiphysics software has been used to design this PCF fiber. Simulated outcomes show a particularly an UML deficit of 0.014 cm−1, power fraction in the core area (CA) and large effective area (EA) of 72%, and 5.90 × 10−8 m2 respectively at 1 terahertz (THz) frequency. Also, other aspects of optical fiber for THz signal banquet with confinement loss (CL), scattering loss (SL) and V-parameter have been calculated here. Moreover, our proposed SM-PCF shows single-mode propagation by V-parameter pointer over 0.80–3 THz frequency. So, we can say that our designed PCF fiber will be suitable for various effective communication areas at the terahertz (THz) spectrum. [ABSTRACT FROM AUTHOR]

A new type of high birefringence terahertz (THz) band photonic crystal fiber (PCF) is proposed. D-shaped air holes are introduced into the core of the PCF and the cladding near the core. Some important parameters of this waveguide were researched in the range of 0.6–1.2 THz. The simulation results show that the proposed fiber has a high birefringence of 0.0425 at 0.7 THz. In addition, the confinement loss and the effective mode area are respectively 6.63 × 10−7 dB/m and 0.77 × 105 μm2, when the operating frequency is 1 THz and the high birefringence of 0.04 is maintained. At the same time, very low bending loss and near zero flat positive dispersion are obtained. And has single-mode operating characteristics in the entire research frequency range. The PCF structure will provide new solutions for the application of THz waves and the design of THz waveguides. [ABSTRACT FROM AUTHOR]

An AlGaAs based standard photonic crystal fiber structure is reported for low dispersive nonlinear optics applications. By employing a finite element solver with perfectly matched layer boundary condition, the key propagation characteristics are investigated over a broad wavelength span (1–5 μm) by taking the different air filling fraction values. The proposed work provides an effective fundamental mode area of 7.30 μm2 with nonlinearity in the order of 8.325 W−1m−1 at a low absorption wavelength of 1.55 μm and zero-dispersion wavelength close to 3 μm. [ABSTRACT FROM AUTHOR]

In this study, design and transmission characteristics of a special type of photonic crystal fiber (PCF) geometry namely, circular-lattice photonic crystal fiber (C-PCF) structure are presented. The cladding of the structure consists by a cylindrically symmetrical distribution of air-holes in the silica background and the core is created by omitting one air-hole at the center. The structure provides high degree of flexibility in the fiber design and hence tailorable modal properties. Structural dependence of transmission characteristics of the geometry is numerically investigated by using finite difference mode convergence algorithm. The wavelength responses of fiber parameters, such as effective refractive index, chromatic dispersion, mode-effective area, and nonlinear coefficient of the structure are systematically investigated. Besides, effective V-parameter and single-mode operation of the fiber are also evaluated and discussed. The simulation results show the possibility of large negative dispersion and dispersion flattened nature of the geometry. [ABSTRACT FROM AUTHOR]

A hybrid structured honey-comb photonic crystal fiber sensor is designed to detect the sensitivity of methyl salicylate (C8H8O3), arsenic trichloride (AsCl3), and ethylbenzene (C8H10) analytes. The cladding portion of the proposed structure consists of both circular and hexagonal holes in the form of a hexagon with a honeycomb arrangement. Moreover, the structure has a circular core with the chosen analyte. The design is investigated in the scope of wavelength ranging from 0.4 to 1.75 µm. The hybrid photonic crystal fiber sensor displays a sensitivity of 85.05%, 87.89%, 82.73% for methyl salicylate, arsenic trichloride, and ethylbenzene, respectively at 1.550 µm. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the problem of using laser radiation in the supercontinuum mode in fiber optical gyroscopes. To achieve this goal, the following tasks were solved in the work. The physics of the process of measuring the angular velocity of an object based on the Sagnac effect is described. The factors influencing the resolution of the gyroscope are analyzed. These factors include fractional noise, unavoidable noise, and noise due to backscatter in the fiber, which can be minimized by using photonic crystal fibers and a broadband radiation source. It is proposed to use an optical supercontinuum (optical comb) as such a source. Thanks to its ultra-wide radiation spectrum, precision frequency reproduction accuracy, high radiation stability and femtosecond pulse duration, supercontinuum is considered as a promising radiation source in ranging, hyperspectral spectroscopy and imaging, tomography, and low-coherence white light interferometry. In the work of Lpischan, the physics of the supercontinuum generation process, its main characteristics. An analysis of the possibility of using an optical comb in optical gyroscopy has been carried out. Mathematical modeling of the influence of optical fiber characteristics and supercontinuum parameters on the sensitivity of a fiber gyroscope was carried out. The results of the work indicate the promise of further research on the creation of a photonic crystal fiber-optic gyroscope using supercontinuum laser radiation. [ABSTRACT FROM AUTHOR]

The research field of photonic crystals (PhCs) remains active on a global scale. PhCs, which are periodic optical nanostructures with the characteristics of excellent light field confinement and numerous varying degrees of freedom, provide a solid foundation for controlling the movement of light. Periodic variation of the index of refraction in two or three spatial dimensions with a substantial high-to-low ratio generates a number of intriguing phenomena and enables a variety of potential functionalities. Recently, intriguing devices based on PhCs, such as Y-branches, small-diameter bent waveguides, and miniature resonator cavities, have been proposed and extensively utilized. PhC waveguides are considered ideal candidates for a variety of applications, such as in power splitters, logic gates, sensing and communication fields, etc. These exceptional characteristics may facilitate the development of a dense integrated circuit. However, PhC technology is still relatively new and therefore requires additional effort to fully exploit it. This paper reviews the most popular and essential optical components based on PhCs, including power splitters, modulators, polarization maintaining devices, sensors, and lasers, to summarize the most recent developments relating this hot topic. These devices have superior performance and a smaller footprint compared to conventional photonic devices. [ABSTRACT FROM AUTHOR]

This paper combines molybdenum dioxide (MoO2) instead of the gold film with photonic crystal fiber (PCF) for the first time. A novel C-type micro-opening surface plasmon resonance (SPR) optical fiber sensor coated with MoO2 nanofilm is proposed. The polarization and sensing characteristics of the sensor coated with plasma film on the outer surface of the polished optical fiber are numerically analyzed by the finite element method (FEM). The simulation results show that when the plasma material deposited by the optical fiber micro-opening is noble metal gold, the sensor can realize the sensing detection of the refractive index of the analyte from 1.33 to 1.39, and the average wavelength sensitivity in the x-polarization direction reaches 1107 nm/RIU. It is most noteworthy that when the plasma coating material of the optical fiber is replaced by metal oxide MoO2, the sensor can realize the sensing detection of the refractive index of the analyte from 1.31 to 1.37, and the average sensitivity of the x-polarization direction can reach 4821 nm/RIU. By comparison, we can know that the sensor coated with plasma material MoO2 has excellent sensing characteristics. This research is of great scientific significance for expanding the application range of MoO2 materials and promoting the development of photonic crystal fiber sensors coated with new materials. [ABSTRACT FROM AUTHOR]

In the present study, a rectangular-shaped photonic crystal fiber-based sensor has been proposed for the identification of various types of cancer cells. Finite element method-based COMSOL multiphysics software has been used to evaluate the performance of the sensor. The variation in the refractive index has been used for the identification of cancer cells. The simulation of the accessed model has been achieved for various cancer cells such as MCF-7, Jurkat, PC-12, HeLa, MDA-MB-231, and basal detectors. The values of birefringence, effective refractive index, relative sensitivity, nonlinearity, and effective area are obtained for MCF-7, Jurkat, PC-12, HeLa, MDA-MB-231, and basal cells for the optimum + 5% case, optimum case, and optimum-5% case in x and y directions, respectively. The proposed photonic crystal fiber-based sensor has been utilized for the identification of breast cancer type II, blood cancer, adrenal gland cancer, cervical cancer, breast cancer type I, and skin cancer. [ABSTRACT FROM AUTHOR]

Six high-performance photonic crystal fiber polarization filters based on surface plasmon resonance are proposed and studied by Matlab and Comsol Multiphysics based on finite element method. Dual D structure is adopted in order to improve birefringence and increase coupling strength between surface plasmon and fiber core light energy. The characteristics of loss, filtering, and extinction ratio were studied, including six material situations: gold, silver, aluminum, gold and graphene, silver and graphene, aluminum and graphene. The mode coupling phenomenon and the influence of metal thickness on optical fiber devices are analyzed. Research result shows that the proposed fibers have good filtering ability, and when the fiber length is 2 mm, the extinction ratio can reach 4520 dB. [ABSTRACT FROM AUTHOR]

In this study, a photonic crystal fiber (PCF) sensor is proposed for refractometric sensing. The proposed PCF sensor includes a single rectangular core and 32 rectangular air holes in the cladding region that have the same width and height as the core rectangle. The fiber substance used is Zeonex. The finite element-based COMSOL 5.6 program is used to numerically analyze the model. The simulation confirms the suggested PCF capability to identify the analyte samples with extremely high sensitivity. A frequency range of 1.5–3.0 THz was adopted. At an operating frequency of 2.8 THz, many performance metrics are calculated. Extremely low effective area (6.3575 × 104 µm2), effective material loss (0.00222 cm− 1) and confinement loss (0.52772 × 10− 14) have been obtained with the proposed sensor. Extremely high-power factor (98.128%), birefringence (3.3 × 10− 3), numerical aperture (0.23319) and relative sensitivity (98.876%) have been also obtained with the current PCF sensor. Moreover, the fabrication possibility of the proposed sensor is further assured by the PCF design's simplicity. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a D-type highly sensitive surface plasmon resonance (SPR)sensor based on multilayer films coated with photonic crystal fiber (PCF). Silver was selected as the plasmon material because its SPR spectrum is sharper than gold. Meanwhile, we used the titania (TiO2) as the second layer film since it could prevent the oxidation of silver and enhance the SPR effect. We simulated the refractive index sensing performances using the finite element method (FEM). This paper optimized the air hole size, polishing depth, silver film thickness, and TiO2 thickness. The multilayer film structure showed a significant improvement in the wavelength sensitivity of the sensor. The result showed that the maximum sensitivity reached 11,000 nm/RIU, which was increased by 139% compared with a single silver film. The sensor was suitable for accurately detecting the medical treatment and organic chemicals because of its high sensitivity and FOM. [ABSTRACT FROM AUTHOR]

Birefringence is a critical aspect in fiber optic-based applications, particularly in preserving polarization and achieving nonlinear-based phase matching conditions. This study proposes a new highly birefringent nonlinear photonic crystal fiber that is simple and compact. The proposed fiber structure features only six air holes in the cladding to confine light at the core, resulting in a more compact design. The fiber exhibits an observed birefringence of about 0.0113, a nonlinear coefficient of about 86.64 W−1 km−1, and a confinement loss of about 10−18 dB/km. The measured V-parameter of about 1.108 ensures single-mode operation of the proposed fiber. The compact design and promising properties of the proposed fiber structure make it suitable for a variety of fiber optic-based applications. [ABSTRACT FROM AUTHOR]

In the present study, a photonic crystal fiber with a simple design and low losses in the range of terahertz broadband pulse was designed. The proposed structure of this study consisted of a large central air core arranged by three rings of air holes in a regular hexagonal pattern in a uniform Teflon matrix. The refractive index of Teflon, which was made of polymer, was 1.44. The conduction in this fiber was achieved using photonic band gap (PBG) only for a certain range of non-zero values. The simulation results showed that at the wavelength of 174 µm with a central hole diameter of 2.9Ʌ (Ʌ = 300 µm), the lowest confinement losses equal to 0.2 dB/m occurred and the dispersion parameter was 1.2 ps/nm km. [ABSTRACT FROM AUTHOR]

Optical coherence tomography (OCT) is a new technology for high-resolution cross-sectional images of biological tissues. In this research, we have designed a photonic crystal fiber (PCF) made of silica with proper dispersion characteristics about the center wavelength of 800 nm to simulate supercontinuum generation (SCG) which is desired for a high-resolution OCT in ophthalmology. Several types of PCFs with different air-hole diameters are designed where squared hyperbolic secant pulses are provided to simulate SCG by solving the generalized nonlinear Schrodinger equation (GNLSE) via split-step Fourier method. To obtain more accurate SCG, dispersion coefficients up to 9th order, Raman scattering and self-steepening are taken into account. We examine the impacts of air-hole diameter, input pulse width and pulse peak power on the SCG bandwidth as well as the OCT resolution through which suitable parameters for maximum axial resolution in ophthalmology are determined. [ABSTRACT FROM AUTHOR]

In this paper, a D-type photonic crystal fiber (PCF) with Zeonex material as the substrate and polyvinylidene fluoride (PVDF) material as the surface plasmon resonance (SPR) excitation layer is proposed for biosensing in the terahertz (THz) band. Analyzed with a finite element method, the proposed biosensor has shown excellent sensing properties for analyte refractive indices ranging from 1.32 to 1.45. With a maximum sensor resolution of 8.40 × 10−7 refractive index unit (RIU) and a figure of merit of 39.42 RIU−1, the maximum wavelength sensitivity and amplitude sensitivity can reach 335.00 μm/RIU and −66.01 RIU−1, respectively. A ±2% fabrication tolerance analysis is also performed on the biosensor to prove its practical feasibility. We conclude that our proposed PCF biosensor utilizing PVDF-excited SPR can provide high sensitivity, and thus a compact, label-free, and convenient solution for biomedical liquid sensing in the THz band. [ABSTRACT FROM AUTHOR]

In this regard, we directed a theoretical study with numerical simulations. This study allowed us to illustrate how a photonic crystal fiber (PCF) structure could divide an optical signal. One of the most fundamental components used to construct photonic integrated circuits (PIC) is the splitter, which is using light coupling between the cores as a control until the output ports by using pure silica to replace some air-hole zones along the PCF axis and split the single signal on two ports with almost equal intensity in each port. Optical interconnects are one of the most basic components of integrated optics, and splitters for photonic power are a key element of a connected family. With the least amount of loss, a competent photonic splitter can guide light input of a certain wavelength to several ports at various intensities. [ABSTRACT FROM AUTHOR]

Transmission window is a major concern in selecting the background material of photonic crystal fiber for supercontinuum generation. In this work, Zinc-Germanium Diphosphide (ZnGeP2) based single material photonic crystal fiber has been proposed with high nonlinearity and low confinement loss for near and mid-infrared supercontinuum generation. As single material is used, hence the concerned difficulties for choosing separate materials for core and cladding is eliminated. Again, the light transmission window of ZnGeP2 is very large (700 nm – 13000 nm). Optical properties like dispersion, numerical aperture, effective area, nonlinearity and confinement loss are analyzed and demonstrated for a wavelength range of 1000 – 5000 nm. COMSOL software is used to design the fiber and finite element method (FEM) is adopted for numerical analysis. The proposed fiber presents low and flattened dispersion in the range of 2250 – 5000 nm, nonlinearity of the order of 104 W–1km−1 and confinement loss of the order of 10–9 dB/m. The fiber is then used for supercontinuum generation in both near and mid-infrared range and an unprecedented bandwidth of 31000 nm has been achieved which may be pragmatic for outstanding medical applications.

The advent of nanotechnology has motivated a revolution in the development of miniaturized sensors. Such sensors can be used for radiation detection, temperature sensing, radio-frequency sensing, strain sensing, and more. At the nanoscale, integrating the materials of interest into sensing platforms can be a common issue. One promising platform is photonic crystal fibers, which can draw in optically sensitive nanoparticles or have its optical properties changed by specialized nanomaterials. However, testing these sensors at scale is limited by the the need for specialized equipment to integrate these photonic crystal fibers into optical fiber systems. Having a method to enable rapid prototyping of new nanoparticle-based sensors in photonic crystal fibers would open up the field to a wider range of laboratories that could not have initially studied these materials in such a way before. This manuscript discusses the improved processes for cleaving, drawing, and rapidly integrating nanoparticle-based photonic crystal fibers into optical system setups. The method proposed in this manuscript achieved the following innovations: cleaving at a quality needed for nanoparticle integration could be done more reliably (≈100% acceptable cleaving yield versus ≈50% conventionally), nanoparticles could be drawn at scale through photonic crystal fibers in a safe manner (a method to draw multiple photonic crystal fibers at scale versus one fiber at a time), and the new photonic crystal fiber mount was able to be finely adjusted when increasing the optical coupling before inserting it into an optical system (before, expensive fusion splicing was the only other method).

We numerically analyze a dual-core gold coated photonic crystal fiber (PCF) biosensor based on surface plasmon resonance that can be used for remote sensing applications in place of the traditional prism-based biosensor. Chemically stable active plasmonic material gold (Au) are positioned outside the fiber structure as a sensing layer to facilitate the construction of the sensor. From finite element method (FEM) based simulation, it is shown that the proposed sensor has the maximum wavelength sensitivity of 5000 nm/RIU. In addition, the amplitude sensitivity of the sensor is 267.66 RIU−1 with the resolution of 2.00 × 10−5 RIU−1 having sensing range of analyte refractive index 1.30 to 1.40. The suggested two-ring dual-core PCF sensor can be used to detect biological analytes, organic compounds, biomolecules, and other unidentified analytes due to its high sensitivity, enhanced sensing resolution, and suitable linearity properties. The proposed sensor has high sensitivity and wide operating range; from visible to mid-infrared which enables the detection of various biomolecules with different absorption or fluorescence spectra. Overall, the unique combination of structural design and optical properties make hexagonal PCF biosensor a promising and innovative platform for advanced and high-performance biosensing applications.

In this paper, a dual-core photonic crystal fiber (DC-PCF) sensitivity sensor filled with magnetic liquid is introduced and investigated with the finite element method (FEM). To regulate the energy coupling involving the two cores, the magnetic fluid is filled into the pore between the two cores. To adjust the coupling between the supermodes in the DC-PCF, the refractive index (RI) of the air hole filled magnetic fluid may change due to the external magnetic field. This specifically created a magnetic fluid-filled DC-PCF; the magnetic fluid-filled hole is not used as the core for energy transmission, thus avoiding transmission loss. The dip wavelength and the magnetic field displayed an excellent linear connection between 80 and 260 Oe, depending on the numerical data. The detection sensitivity of the magnetic field reached 515.75 pm/Oe at a short fiber length of 482 µm. The designed magnetic fluid-filled DC-PCF has high sensitivity and small volume and has great application prospects in magnetic field detection in the medical and industrial fields. [ABSTRACT FROM AUTHOR]

This study presents a new square‐lattice photonic crystal fiber (PCF) with a nitrobenzene core. Considering the non‐uniformity of the air hole diameter, this new design allows the characteristic quantities to be optimized simultaneously to ensure near‐zero dispersion, a small effective mode area, and low loss for efficient spectral broadening. The spectrum broadens significantly at peak powers many times lower than in previous studies. Based on the obtained results, two optimal PCFs are proposed and validated in detail for supercontinuum generation (SCG). The first fiber #F1 operates in an all‐normal dispersion regime with a pump wavelength of 1.3 µm.It produces a spectral supecontinuum (SC) from 0.726 to 1.649 µm with a pulse duration of 90 fs and a peak power of 133 W. Meanwhile, the second fiber #F2 operates in anomalous dispersion regime with a pump wavelength of 1.61 µm. With a low peak power of 300 W and a pulse duration of 150 fs, the fiber #F2 provides SC generation with bandwidth from 0.805 µm to 3.970 µm. The proposed fibers are suitable for all‐fiber SC light sources, respectively, and may lead to new low‐cost all‐fiber optical systems. [ABSTRACT FROM AUTHOR]

This research presents a novel link between refractive index sensing and spectroscopy by designing a "photonic crystal fiber" based "refractive index ( RI )" sensor. The proposed sensor is based on the "surface plasmon resonance" phenomenon. The sensor monitors the transformer oil ( To ) moisture content as moisture depletes its quality. The change in the moisture content changes the RI of the transformer oil. Thus, the presented sensor can identify the minimal change in the RI of the To . The sensor is designed to operate in the RI range of 1.33 - 1.34 RIU , with a step size of 0.002. Using the wavelength interrogation method, the proposed sensor's wavelength sensitivity is 25,000 nm/RIU and 22,500 nm/RIU along X-polarization (X-pol.) and Y-polarization (Y-pol.), respectively. The amplitude interrogation technique is used to calculate the amplitude sensitivity obtained from the proposed sensor, which is 17080 RIU - 1 and 18690 RIU - 1 corresponding to X-pol. and -pol., respectively. The sensor resolution of the sensor is 4.00 × 10 - 6 RIU and 4.44 × 10 - 6 RIU corresponds to X-pol. and Y-pol., respectively. Full-width half maximum obtained from the proposed sensor is 73 nm and 55 nm for X- and Y-pol. , respectively. The figure of merit obtained from the presented sensor is 342.46 RIU - 1 and 409.09 RIU - 1 for X - and Y-pol., respectively. Thus, the prospective sensor can act as an ideal device for the quality assessment of To . [ABSTRACT FROM AUTHOR]

In this work, we study the generation of ultrashort femtosecond laser pulses in photonic crystal fibers through the widely used symmetric split-step Fourier method (S-SSFM). The results are compared with the method of fourth-order Runge-Kutta method (RK4) as the most recognized and powerful method in the analysis of the evolution of ultrashort femtosecond laser pulses. The results show that although S-SSFM is a widely used method, its accuracy decreases for the selected relatively large step sizes of ∆𝑧 in comparison with RK4. In contrast, the accuracy of the mentioned methods becomes closer to each other by selecting relatively small step sizes of ∆𝑧. [ABSTRACT FROM AUTHOR]