SQU Journal for Science, 2022, 27(2),119-124 DOI:10.53539/squjs.vol27iss2pp119-124 Sultan Qaboos University 119 Optical Properties of Photonic Crystal Fibers with Fluid Cores Mohammed Salim Jasim Al-Taie Gifted Guardianship Committee, Directorate of Education, Misan, Iraq *Email: mohammed.altaie@iraqiggc.edu.iq. ABSTRACT: The objective of this research is to compare pulses travelling through different photonic crystal fiber cores (DPCFC) using both finite element method (FEM) /split step Fourier method (SSFM). A unique DCPCF design with exceptionally high non-linearity has been introduced to achieve ultra-high pulse amplitude. Via a generalized non- linear equation, we evaluate the refractive index ratio and dispersion, for each type which is used, as well as output amplitude for different cores in different photonic crystal fiber core by utilizing the solution for the nonlinear Schrodinger equation (NLSE). Lastly, the findings are compared to different photonic crystal fiber design parameters. This paper provides a photonic crystal fiber design consisting of multiple liquid cores and theoretically solved non- linear equations. It was discovered in this design that the refractive index of propylene glycol (C3H8O2) is greater than ethylene glycol’s (C2H6O2), and that both are far greater than silica's refractive index (SiO2). Propylene (C3H8O 2 ) has a lower dispersion than ethylene glycol (C2H6O2) and silica (SiO2). The output amplitudes of (C3H8O2) and (C2H6O2) were then shown to be substantially bigger than the output amplitudes of (SiO2) with respect to distance and time. This emphasizes the need for using certain liquids as cores in holey fibers, dependent upon their use. Keywords: Photonic crystal fiber; Split-Step fourier; Finite element method; Non-linear schrodinger equation; Solution pulse. بلورة الفوتونية ذات النوى السائلة متأللياف اللالخصائص البصرية محمد سالم جاسم الطائي فورييه ذات ستخدام طريقة العناصر المحدودة وطريقة إوى ألياف بلورة فوتونية مختلفة بعبر ن المتنقلةالهدف من البحث هو مقارنة النبضات :صلخمال لة ال خطية معممة ، تقديم تصميم جديد من هذا النوع بوجود ال خطية عالية بشكل استثنائي لتحقيق سعة نبضة فائقة. من خالل معادلمنقسمة , تم الخطوط ا ختلفة. اعتمادا على معادلة شرودنكر الالخطية. أخيًرا ، تمت مقارنة النتائج بمعايير التصميم الم نسبة معامل اإلنكسار و التشتت لنوى مختلفه ، تم حساب تم اكتشاف في هذا قدم هذا البحث تصميًما من الياف بلورة فوتونية والمتكونة من نوى سوائل متعددة معتمدة على معادالت ال خطية تم حلها نظريًا. حيث ليكا, كما يظهر أن البروبيلين جاليكول التصميم أن معامل انكسار البروبيلين جليكول أكبر من اإليثيلين جليكول، وكالهما أكبر بكثير من معامل انكسار السي لسوائل قيد الدراسة ومقارنتها مع السليكا حيث ظهر ان األتساع اكما تم عرض نسبة اتساع الخرج للنبضة في ،له تشتت أقل من اإليثيلين جاليكول والسليكا لزمن . وهذه النتائج تؤكد الحاجة إلى استخدام سائل معين في قلب ليف البلورة للبروبيلين جاليكول و اإليثيلين جاليكول اكبر بكثير من السليكا مع المسافة وا التطبيقات المختلفة. في الستخدامها الفوتونية لزيادة كفاءتها واداؤها خطية ، نبضة سوليتون.الال فورييه المنفصل ، طريقة العناصر المحدودة ، معادلة شرودنجر طريقة، بلورة الفوتونيةلياف الأ :مفتاحيةالكلمات ال MOHAMMED SALIM JASIM AL-TAIE 120 1. Introduction luid- filled core photonic crystal fibers (FCPCFs) have received a great deal of interest in recent years because of the wide range of uses they might have in a variety of industries [1-15]. Filling the core section of the PCF with fluids results in unique optical features such as wideband single-mode guiding, ultra- flattened dispersion, large birefringence, huge or ultra- tiny effective areas , should it be tailored mode area, significant nonlinearity, and so on [16]. Using various fluids to fill in the core of PCFs, should it be a multiple assessment refractive index may be obtained. By filling the core with different fluids, several characteristics of PCFs, including effective area, dispersion, and nonlinearity, may be adjusted [17-20]. The variation in refractive index between its core and the cladding in a FCPCF is significantly greater than in a silica core PCF[21-22]. The effective area of the modes of the FCPCF is inversely related to the fiber's nonlinearity [23-24]. It is generally understood that the size of the air hole, and therefore its effective area, is the control parameter in a PCF for adjusting nonlinearity and dispersion. Many academics are interested in the soliton pulse in PCFs with various structures, which is one of their applications [25-27]. PCFs have a higher dispersion than silica fibers, according to research. As a result, the dynamics of solution may be investigated on centimeter-length scales. The purpose of this study is to develop the proposed PCF design for ultra-high pulse amplitude. We use the finite element technique to compute the dispersion and nonlinear coefficients in this work. The technique of computation of the pulse amplitude in a PCF is investigated using the finite element technique, which solves the wave equations, and the Split-step method, which solves the NLSE with an exponentially decreasing dispersion profile for constant design parameters for various core fluids. 2. High Nonlinear Photonic Crystal Fiber Design We computed the transmission constant of two distinct fluid photonic crystal fibers (PCFs ) with propylene (C3H8O2) and ethylene glycol ( C2H6O2) in the core region. The finite element method (FEM) is a commonly utilized mathematical technique for evaluating the field of electromagnetic radiation of PCF travel modes. PCF's effective refractive index was investigated using FEM. The PCF was determined by the diameter of the air hole (Figure 1, d), the distance between the air holes (Figure 1, Λ), and number of air holes (Figure 1, N). The investigated PCF had a lot of nonlinearity, and the parameters were Λ= 3𝜇𝑚, d = 1.68 𝜇𝑚, N = 6. Following up on these results, a new PCF was created by filling the core region with fluid. Figure 1. (a) Longitudinal section of the photonic crystal fiber, (b) Cross-section of the photonic crystal fiber. By using finite element method (FEM), the effective refractive index of the fluid filled PCF is greater than that of the PCF with a solid core structure because the refractive index of propylene glycol and ethylene glycol is higher than that of silica, as shown in Figure 2. F (b) (a) OPTICAL PROPERTIES OF PHOTONIC CRYSTAL FIBERS WITH FLUID CORES 121 Figure 2. The relationship between the refractive indices of SiO2, C3H8O2 and C2H6O2. The group velocity dispersion (GVD) of propylene glycol and ethylene glycol was determined using the transfer function. Figure 3 illustrates the variance in GVD as a function of λ, for different fluids with d = 1.68m and Λ = 3m. Figure 3. The dispersion of cores consisting of SiO2, C3H8O2, and C2H6O2. The computed wavelength dependency of the nonlinearity for various core regions in PCFs is shown in Figures 2 and 3, where the nonlinearity is calculated on a logarithmic scale due to the higher fluctuation in FCPCFs than that found in silica core PCFs. The greatest effective area a PCF can support is determined by the fluid in the core. The effects of the intensity dependent nonlinearity is shown to be minimized when the effective area is raised. The nonlinearity of the FCPCF is a few hundred times greater than that of the silica core PCF, as seen in Figure 3. 2. Pulse Amplitude in Photonic Crystal Fibers Consider the following NLSE of the form in order to understand the mechanics of pulse amplitude in PCF[28- 32]. (𝜕𝐴 𝜕𝑧⁄ ) − ∑ ( 𝑖 𝑛+1 𝑛! ⁄𝑛≥2 ) 𝛽𝑛 ( 𝜕𝑛 𝐴 𝜕𝑇𝑛⁄ ) = 𝑖𝛾⃓𝐴 2⃓𝐴 (1) and MOHAMMED SALIM JASIM AL-TAIE 122 𝐴(0, 𝑇) = √𝑃° sech ( 𝑇 𝑇° ⁄ ) exp (𝑖𝛼 𝑇 2 2⁄ ) (2) where A is the wave's slowly varying envelope intensity, z is the fiber's lengthwise position in meters, and T is the reference frame's duration in seconds. The parameter (𝛾) is used to indicate the Kerr nonlinear factor. Figure 4 illustrates the pulse amplitude of propylene glycol and ethylene glycol as a function of time at a wavelength of 835 nm, and Figure 5 depicts the impact of core fluids on pulse amplitude as a function of length in PCF, after solving Equation (1) theoretically using SSFM. Figure 4 shows a sequence of intensity pulses for each core material. It is obvious from this graph that the amplitude of the pulses for propylene glycol and ethylene glycol are larger than that of silica, which is lower, and that it is higher for PCF with a fluid core than for PCF with a silica core. Because FCPCF can reach extremely high nonlinearity, very high pulse amplitude may be easily achieved by filling the core area with fluid, as illustrated in Figures 4 and 5. As a result, it is worth noting that our newly developed PCFs are very well suited for constructing nonlinear devices, in addition to increasing the amplitude of the pulses. Conclusion In conclusion, the pulse amplitude in FCPCF with C3H8O2, C2H6O2 and SiO2 fluid cores was investigated using a FEM and an SSFM. In comparison with the amplitude ratio of silica-core PCF, we have successfully proven that the novel fluid core photonic crystal fiber we have developed can reach ultra-high pulse amplitude. In addition, the refractive index and dispersion for different liquid cores were studied. The objective of this research was to compare output pulse propagation through different cores of holey fiber (DCHF) using both finite element (FEM) and split step Fourier methods (SSFMs) to solve the nonlinear Schrodinger equation. In conclusion, it turns out that the pulse amplitude in different cores of holey fiber, which consist of C3H8O2 and C2H6O2, is much larger than the amplitude ratio of silica-core photonic crystal fiber. This gives great importance to using certain types of liquids as cores in holey fiber, depending upon the various uses and applications they will be put to, and according to the designers' needs. Conflict of interest The author declares no conflict of interest. Acknowledgment Many thanks to Professor H.A. Sultan. who read my numerous revisions and helped make some sense of the confusion. Also thanks to my family members, who offered support. 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