Saghaei's papers published in 2020

[1] S. Naghizade and H. Saghaei, “A novel design of all-optical 4 to 2 encoder with multiple defects in silica-based photonic crystal fiber,” Optik, vol. 222, p. 165419, 2020, doi: 10.1016/j.ijleo.2020.165419.

An encoder logic gate is a combinational circuit that performs the coding operation on the input binary data, and 2n input lines are encoded with n bits. In this paper, we present a new design of a high-speed all-optical 4 to 2 encoder using a solid-core photonic crystal fiber (PCF) composed of pure silica. The proposed structure consisting of an optical buffer and two optical OR gates has four input ports and two output ports in a square lattice of PCF. The plane-wave expansion method is used to compute the band structure of the encoder, and the beam propagation method is applied to calculate the transmission and the electric field distribution of optical light inside the device. We demonstrate that the proposed 4 to 2 encoder can operate in the C-band, ranging from 1530 nm to 1565 nm, which is an appropriate device for telecommunication applications. The numerical results demonstrate that the normalized transmission values less than 0.02 % and greater than 95 % are supposed to be logic 0 and logic 1, respectively. The maximum delay of the encoder is 0.3 ps, and its total footprint is 50 μm × 30 μm×3 mm; thus, due to the relatively simple and low-cost fabrication of PCFs and their applications in photonics-based systems, the proposed device can be used in optical communications and networking.

[2] A. Mostafaeipour et al., “Statistical evaluation of using the new generation of wind turbines in South Africa,” Energy Reports, vol. 6, 2020, doi: 10.1016/j.egyr.2020.09.035.

In view of the latest status and the potential of developing wind energy in South Africa, the present study aims to perform technical–economic–environmental​ analysis on a wind turbine system with HOMER software using the 20-years average data of the wind speed obtained from NASA’s database, for providing the electricity to residential buildings. The results showed that the Port Elizabeth station, had the lowest levelized cost of electricity (LCOE) with the value of -0.363 $/kWh when using the EOLO wind turbine, and the Bloemfontein station had the highest LCOE with the value of 1.601 $/kWh when using the Turby wind turbine. The results from the step-wise assessment ratio analysis (SWARA) weighting method demonstrated the wind penetration, total production, and capital cost as the most important sub-indices with the weights of 0.106, 0.095, and 0.091, respectively. Using the additive ratio assessment (ARAS), weighted sum method (WSM), and weighted aggregated sum product assessment (WASPAS) techniques, the cities under study were ranked, and the cities of East London and Bloemfontein were identified as the most suitable and the most unsuitable stations for the use of household-scale wind turbines, respectively.

[3] M. Aliee, M. H. Mozaffari, and H. Saghaei, “Dispersion-flattened photonic quasicrystal optofluidic fiber for telecom C band operation,” Photonics and Nanostructures - Fundamentals and Applications, vol. 40, p. 100797, 2020, doi: 10.1016/j.photonics.2020.100797.

Photonic quasicrystals are of particular interest for waveguiding applications because of their beneficial advantages over conventional photonic crystals, such as higher-order rotational symmetry and more isotropic Brillouin zone. In this work, by use of a 12-fold symmetric photonic quasicrystal lattice and an optofluidic infiltration approach, we sought to design a hollow-core fiber for telecom C band operation. The simulation results demonstrate a wide flat dispersion range around the zero-dispersion wavelength of 1550 nm and an ultralow confinement loss of 2.6 × 10-7 dB/m, whereas the maximum effective mode area attained in the simulations is approximately 5.5 μm2.

[4] M. Hosseinzadeh Sani, A. Ghanbari, and H. Saghaei, “An ultra-narrowband all-optical filter based on the resonant cavities in rod-based photonic crystal microstructure,” Optical and Quantum Electronics, vol. 52, no. 6, p. 295, 2020, doi: 10.1007/s11082-020-02418-1.

In view of the large scientific and technical interest in the frequency-selective all-optical devices, and some optical filters limitations, we focus on the design and analysis of a novel ultra-narrowband all-optical filter. The proposed structure consists of input/output waveguides and a resonator in a microstructured photonic crystal that encompasses silicon rods. We study the effects of the variations of rod radius, the lattice constant, and the refractive index of the filter on the resonance wavelength, quality factor, transmission, and full width at half maximum (FWHM) by solving Maxwell’s equations using the finite-difference time-domain method. The numerical results show that the proposed filter with a lattice constant of a = 540 nm, central resonant rod radius of 216 nm, and the rod radius of r = 0.2a has a resonant wavelength of λr = 1253 nm, the quality factor of Qf = 3288, FWHM of 0.26 nm and broad free spectral range of FSR = 790 nm while this filter for r = 0.26a has λr = 1552 nm, Qf = 5542, FWHM of 0.28 nm, and FSR = 720 nm. Some promising characteristics, such as its short propagation time and a small area of 102.6 µm2 make this optical filter an interesting candidate for use in photonic integrated chips.

[5] S. Naghizade and H. Saghaei, “Tunable graphene-on-insulator band-stop filter at the mid-infrared region,” Optical and Quantum Electronics, vol. 52, no. 4, p. 224, 2020, doi: 10.1007/s11082-020-02350-4.

This paper presents a novel graphene-on-insulator (GOI) band-stop filter in the mid-infrared region. The finite-difference time-domain method is used to model our GOI basic and advanced filters and calculate their transmission spectra for different graphene layers at every gate-source voltage. The numerical results reveal the resonance wavelength, modulation depth, and bandwidth of the advanced filter can be tuned in the range of 11.5 to 30 µm, − 57 to − 60 dB, and 2 to 4 µm, respectively. These results are obtained by variation of the physical parameters, such as the number of overlapped filters, the number of graphene layers, and the applied chemical potential. Our results indicate that the proposed advanced band-stop filter is an excellent device to be used in an ultra-fast active graphene-based plasmonic systems for THz applications.

[6] M. H. Sani, A. A. Tabrizi, H. Saghaei, and R. Karimzadeh, “An ultrafast all-optical half adder using nonlinear ring resonators in photonic crystal microstructure,” Optical and Quantum Electronics, vol. 52, no. 2, p. 107, 2020, doi: 10.1007/s11082-020-2233-x.

Half adder and half subtractor are the basic building blocks of an arithmetic logic unit used in every optical central processing unit (CPU) to provide computational operators. In this paper, we aim to design an ultrafast all-optical half adder based on nonlinear ring resonators. The proposed structure consists of the concurrent designs of the AND and XOR logic gates inside a rod-based photonic crystal microstructure. The linear dielectric rods made of silicon and nonlinear dielectric rods composed of doped glass are used to design the nonlinear ring resonators as the fundamental blocks of a half adder. We demonstrate as the intensity of the incoming light increases, the nonlinear Kerr effect appears, and the total refractive index increases. It diverts the direction of light propagation to the desired nonlinear ring resonator depending on the signal wavelength, the radius of rods and lattice constant. Finally, after several resonances, the light is coupled to the output. Our numerical simulations using a two-dimensional finite-difference time-domain method reveal depending on the light intensity, the maximum and minimum transmissions of the half adder are 100% and 96%, respectively. The calculations also show the delay of the designed half adder is 3.6 ps. Due to the small area of 249.75 µm2, the proposed half adder is an appropriate candidate for photonic integrated circuits used in the next generation of all-optical CPUs.

[7] A. Ghaderian, M. Jahangiri, and H. Saghaei, “Emergency power supply for NICU of a hospital by solar-wind-based system, a step towards sustainable development,” Journal of Solar Energy Research, vol. 5, no. 3, pp. 506–515, 2020, doi: 10.22059/jser.2020.306423.1166.

Equipping hospitals with emergency power supply is crucial. This is especially critical for important wards of the hospital, such as the NICU. Due to the importance of this issue, the present study, for the first time, studies the power supply of vital devices of the neonatal ward in one of the hospitals in Iran. Techno-econo-enviro studies have been performed using HOMER software on 20-year average data. The case study of this article is the Social Security Hospital in Farrokhshahr, Iran, where the system under study uses tree-shaped wind turbines, solar cells, diesel generators and batteries. The use of real data for the electrical consumption of the devices, use of wind and sun data in the form of 20-year averages, and use of up-to-date costs of equipment and consumed fuel, as well as the use of a new generation of the wind turbine, are the advantages of the present study. The results showed that the use of solar energy is superior to the use of wind energy, both economically and environmentally. The cheapest simulated system among 17640 possible scenarios, with the price of each kWh equal to 0.636$, was able to use 18% of the solar energy. In contrast, the cheapest wind turbine-based system was able to use 10% of the wind energy, with the price of every kWh wind electricity equal to 0.917$. The diesel generators are used in all optimal scenarios, which indicates that either the price of solar cells and wind electricity are high compared to the diesel generator, or the intensity of sunlight or wind speed are not high enough. Moreover, compared to the conventional system only consisting of diesel generator, the optimal scenarios of using solar cells and wind turbine, benefit from a reduction in produced pollutants equal to 4.8 and 4 tones/yr, respectively.