Allam, M. A., T. A. Ali, and N. A. D. I. A. H. RAFAT, Broadband dispersion compensation and high birefringence photonic crystal fiber for CWDM/DWDM networks, , vol. 56, issue 6, pp. 1023, 2024. AbstractWebsite

In this study, we propose a new design based on photonic crystal fibers (PCFs) for broadband dispersion compensation in telecommunication networks. The proposed design has a hexagonal structure arrangement of air-holes rings of different diameters between the silica core and the cladding. The PCF properties like effective area, nonlinearity, dispersion slope, confinement loss, and birefringence are reported and discussed. For the best performance we present three designs A, B and C. Simulation results show that the three designs cover the six-telecommunication optical bands O-, E-, S-, C-, L- and U- bands (wavelengths ranging from 1260 to 1675 nm). Design A achieves a large negative dispersion value of about − 1716 ps/(nm.km) with relative dispersion slope equals to that of conventional single-mode optical fibers (SMFs) of about 0.0036 nm−1, which makes it very suitable for long-haul DWDM transmission systems. With a little modification in the core, designs B and C achieve much higher confinement ability and achieve a very large birefringence value for polarization mode dispersion and sensing applications. Design C is engineered to have exact opposite dispersion of SMF with zero dispersion at the wavelength 1310 nm, which makes it a promising design in CWDM transmission system. The numerical values have been investigated using the full vector finite element method.

Kamal, S. M., T. A. Ali, and N. A. D. I. A. H. RAFAT, New designs of 4 × 2 photonic crystal encoders using ring resonators, , vol. 55, issue 3, pp. 261, 2023. AbstractWebsite

Optical encoders are pivotal elements in optical communication applications. There is much need for ultra-compact and high-speed novel designs. This work proposes two new designs of fast, compact 4 × 2 optical encoders using two dimensional photonic crystals. The proposed structures consist of square lattice silicon rods embedded in an air background. The operation of these encoders is based on the wave interference technique. The encoders are designed to help in achieving better performance through increasing the contrast ratio and decreasing the power loss and the return loss. The PWE method is used to analyze the photonic band gap. We used FDTD simulation to obtain the electric field distribution inside each structure and the normalized output power. We prove that the scattering rods improve the directivity of the light toward the desired paths and decrease the backward reflection. The proposed encoders have small footprint areas of 204.8 and 160.4 μm2 and operate at wavelength 1550 nm. They achieve low response time (254 and 163 fs) and high contrast ratio (6.69 and 12.9 dB). Simplicity and compactness of the designs make them suitable for optical signal processors and photonic integrated circuits. Another advantage of these designs is that low input power is enough for the encoders’ operation, because there is no non-linear materials included. Our designs compete with the published works in the last few years especially in their footprint and response time.

Ali, N. M., T. A. Ali, and N. A. D. I. A. H. RAFAT, "Modeling of Perovskite solar cells containing hexagonal-shaped nanorods", Optical and Quantum Electronics, vol. 54, no. 2: Springer, pp. 1–14, 2022. Abstract
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Mousa, M. A., N. A. D. I. A. H. RAFAT, and A. A. E. Saleh, "Toward spectrometerless instant Raman identification with tailored metasurfaces-powered guided-mode resonances (GMR) filters", Nanophotonics, vol. 10, no. 18: De Gruyter, pp. 4567–4577, 2021. Abstract
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AbdelAziz, H. H., T. A. Ali, and N. A. D. I. A. H. RAFAT, "Plasmonic sphere-cube nano dimer for silicon solar cells power absorbance enhancement", Optical and Quantum Electronics, vol. 53, no. 9: Springer, pp. 1–13, 2021. Abstract
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AbdelAziz, H. H., T. A. Ali, and N. A. D. I. A. H. RAFAT, "Plasmonic Yolk-Shell Nano Structures for Solar Cells Absorbance Enhancement", {IOP} Conference Series: Materials Science and Engineering, vol. 956: {IOP} Publishing, pp. 012018, oct, 2020. AbstractWebsite

In this research we study the enhancement in power absorbance of thin film silicon solar cells by plasmonic yolk-shell (YS) nano particles. Plasmonic YS nano particles are simulated on top/bottom position of thin film Si layers. We suggest different structures of YS and simulate the behaviour of such structures using a FDTD simulations. We calculate the limiting photocurrent taking into consideration the enhanced absorbance of the cell. The simulation results show multi-peaked and broad band power absorbance enhancement all over the solar spectrum. The power absorbance enhanced into solar cell by 64% over planar ultra-thin 300 nm Si cell.

Ali, N. M., T. A. Ali, and N. A. D. I. A. H. RAFAT, "A comparison between different structures of perovskite nanorod solar cells", Optik, vol. 202, pp. 163645, 2020. AbstractWebsite

Perovskite is considered a very promising material in solar energy harvesting. Combining the advantages of Perovskite material and nanorod structure, Perovskite nanorod solar cell (PNSC) is believed to achieve a high conversion efficiency with low cost and simple fabrication processes. The rapid increasing efficiency of fabricated PNSC increases the demand for an efficient and accurate modeling that can simulate the parameters performance of the cell and estimate the important outputs. In this work, we simulate different structures of Perovskite nanorod solar cells namely; cylindrical rod, cone rod, inverted-cone rod, and modulated rod. The simulation is based on the finite element method. The material of the modeled cell is TiO2/CH3NH3PbI3 and we optimize the rod length, radius and spacing between rods for all structures to achieve the maximum conversion efficiency. The best efficiency is 18.6% for a cell of cylindrical rod of rod length, rod radius and rods spacing equal 400 nm, 5 nm and 65 nm, respectively.

Ali, N. M., T. A. Ali, and N. H. Rafat, "Two-Dimensional Model for Perovskite Nanorod Solar Cells: A Dark Case Study", IEEE Journal of Photovoltaics, vol. 9, no. 6, pp. 1668-1677, 2019. Abstract
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Hussein, H. M. E., T. A. Ali, and N. A. D. I. A. H. RAFAT, "A review on the techniques for building all-optical photonic crystal logic gates", Optics & Laser Technology, vol. 106, pp. 385 - 397, 2018. AbstractWebsite

Recently, photonic crystals have emerged to contribute in building all-optical computers and optical communication systems. This is due to the urgent need for faster computers and mobiles with high speed processing of data and with higher data transmission rates. In this paper we review the operation of photonic crystal logic gates and depict the different design techniques that produce a wide range of structures realizing the logic functions. We investigate several techniques such as self-collimated beam, multi-mode interference, interference based defect method and nonlinear Kerr materials based gates. As a summary, we compare the various key features of each design and illustrate the advantages and disadvantages of each design technique.