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Among all the different methods to enhance the optical absorption of photovoltaic devices. The plasmonic effect is one the most prominent and effective ways to capture more incident light and also provide good carrier dynamic management. Here, we systematically introduce spherical gold nanoparticles (Au NPs) with different radii in the absorber layer of perovskite solar cells (PSCs). The overall enhanced optical absorption of around 14.20% and 20.02% is achieved for incorporated monolayer and bilayer Au NPs, respectively, in the active layer compared to the pure perovskite layer. Moreover, we employ the metal (Au)-dielectric (TiO2 and SiO2) nanoparticles in the absorber layer. The optical absorption increases as the core-shell size decreases. The optical absorption elevates in both Au@TiO2 core-shell and Au@SiO2 core-shell 17.5% and 3.5%, respectively. These results support superior separation and transfer of charge in the existence of plasmonic NPs. In addition, this study presents a very sophisticated approach in the optical enhancement of PSCs and thus helps to boost the overall photovoltaic device performance.

In the 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.

In this work, we propose two different graphene-covered nanostructured metamaterial absorbers inspired by Penrose tiling. These absorbers allow spectrally tunable absorption within the terahertz spectrum corresponding to 0.2-20 THz. We have conducted finite-difference time-domain analyses to determine the tunability of these metamaterial absorbers. The proposed structures, Penrose models 1 and 2, perform differently from each other due to their design characteristics. Penrose model 2 reaches a perfect absorption at 8.58 THz. In addition, the relative absorption bandwidth calculated at full-wave at half-maximum in Penrose model 2 varies between 5.2% and 9.4%, which characterizes the metamaterial absorber as a wideband absorber. Also, we can observe that as we increase the Fermi level of graphene from 0.1 to 1 eV, the absorption bandwidth and relative absorption bandwidth both increase. Our findings show the high tunability of both models through varying graphene’s Fermi level, the graphene’s thickness, the substrate’s refractive index, and the proposed structures’ polarization. We can further observe multiple tunable absorption profiles that may find applications in designer infrared absorbers, optoelectronic devices, and THz sensors.

Among all the different methods to enhance the optical absorption of photovoltaic devices. The plasmonic effect is one the most prominent and effective ways to capture more incident light and also provide good carrier dynamic management. Here, we systematically introduce spherical gold nanoparticles (Au NPs) with different radii in the absorber layer of perovskite solar cells (PSCs). The overall enhanced optical absorption around 14.20% and 20.02% is achieved for incorporated monolayer and bilayer Au NPs, respectively, in the active layer compared to the pure perovskite layer. Moreover, we employ the metal (Au)-dielectric (TiO2 and SiO2) nanoparticles in the absorber layer. The optical absorption increases as the core-shell size decreases. The optical absorption elevates in both Au@TiO2 core-shell and Au@SiO2 core-shell 17.5% and 3.5%, respectively. These results support superior separation and transfer of charge in the existence of plasmonic NPs. In addition, this study presents a very sophisticated approach in the optical enhancement of PSCs and thus helps to boost the overall photovoltaic device performance.

This paper reports a new design of a tunable optoelectronic half adder/subtractor. Two photonic crystal (PhC) ring resonators are used to realize the proposed structure. Several silicon rods surrounded by silica rods covered with graphene nanoshells (GNSs) form every PhC ring resonator. Setting the chemical potential of GNS with an appropriate gate voltage, we can tune the PhC resonant mode as desired. The plane wave expansion technique is used to study the photonic band structure of the fundamental PC microstructure, and the finite-difference time-domain method is employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We systematically study the effects of physical parameters on the transmission reflection and absorption spectra. By optimizing the geometric dimensions, resonant absorption peaks can be excited at the same time for GNSs. Our numerical results also reveal the maximum time response is about 0.8 ps. The 200 µm2 area of the proposed half adder/subtractor makes it the building block of every photonic integrated circuit. Also, the design of various fast signal processing systems in optical communication networks is possible due to using tunable GNSs in PhC ring resonators. This study can introduce the use of two-dimensional materials in the design and implementation of logic circuits.

In this study, we propose a refractive index sensor for the simultaneous detection of cancer and diabetes based on photonic crystals (PhC). The proposed PhC composed of silicon rods in the air bed arranged in a hexagonal lattice forms the fundamental structure, and two tubes are used to place the cancerous or diabetic samples for measurement. The sensor's transmission characteristics are simulated and analyzed by solving Maxwell's electromagnetic equations using the finite-difference time-domain method for samples under study. The diagnosis of three types of cancer and diabetes is based on changing the samples' refractive index by applying the laser source centered at 1550 nm. Our results demonstrate that the proposed structure's quality factor and sensitivity can be adjusted by changing the sensor's geometry. They reveal that the transmission power is between 91% ~ 100%, depending on the sample. The sensitivity range is also between 1294 and 3080 nm/RIU. The maximum figure of merit is about 1550.11 RIU− 1 with a detection range of 31×10− 6 RIU. The small biosensor area of ​​ 61.56 µm2 makes it a suitable device for various applications in compact photonic integrated circuits.

This paper proposes a new all-optical full-adder design based on nonlinear X-shaped photonic crystal (PhC) resonators. The PhC-based full-adder consists of three input ports, two X-shaped PhC resonators (X-PCRs), and two output ports. The dielectric rods made of silicon and nonlinear rods composed of doped glass are used to design the X-PCRs. Two well-known plane wave expansion and finite difference time domain methods are applied to study and analyze the photonic band structure and light propagation inside the PhC, respectively. Our numerical results demonstrate when the incoming light intensity increases, the nonlinear Kerr effect appears and manages the direction of light propagation inside the structure. The maximum time delay and footprint of the proposed full-adder are about 2.5ps and 663 μm2, making it an appropriate adder for high-speed data processing systems.

This paper reports a new design of a tunable optoelectronic full-adder using two photonic crystal ring resonators (PCRRs). Every PCRR consists of a matrix of silicon rods surrounded by silica rods covered with graphene nanoshells (GNSs). The proposed full-adder is formed by three input ports, two PCRRs, and two output ports for 'SUM' and 'CARRY'. The plane wave expansion technique is used to study the photonic band structure of the fundamental PC microstructure, and the finite-difference time-domain method is also employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We can tune the PhC resonant mode for our desired application by setting the chemical potential of GNSs with an appropriate gate voltage. The numerical results reveal that when the chemical potential of GNSs changes, the switching mechanism occurs and manages the coupling and propagation direction of the input beam inside the structure. We systematically study the effects of physical parameters on the transmission, reflection, and absorption spectra. Our numerical results also demonstrate that the maximum delay is about 0.8 ps. The 663 µm2 area of the proposed full-adder based on two-dimensional materials makes it a building block of every photonic integrated circuit used for data processing systems.

The present study proposes a new type of wavelength division multiplexing as an optical demultiplexer with four, eight, and sixteen output channels. The proposed structure consists of a two-dimensional square array of dielectric rods. The wavelength selection is performed by two defect rods and one defect with a rectangular cross-section. The values of the parameters related to each defect are selected so that the resonant wavelength associated with each output channel is located in the third telecommunication window (1.55μm). It is observed that the proposed demultiplexers demonstrate a high transmission efficiency and low crosstalk. As it is wanted to see just one sharp wavelength at the output of each channel, the quality factor needs to be maximized. Based on the results, the maximum values for demultiplexers with four, eight, and sixteen channels are 19863.89, 14264.57, and 32304.46, respectively. Due to the device’s small size, it can be used for wavelength division multiplexing (WDM) systems in photonic integrated circuits.

In this paper, we report a new design of all-optical full-adder using two nonlinear resonators. The PhC-based full-adder consists of three input ports (A, B, and C for input bits), two nonlinear resonant cavities, several waveguides, and two output ports (for the Sum and Carry). Eight silicon rods and a nonlinear rod composed of doped glass form each resonant cavity. The well-known plane wave expansion technique is used to calculate the photonic band structure. It shows a wide photonic bandgap in the wavelength range of 1365 nm to 2074 nm covering the C and L optical transmission bands. The finite-difference time-domain method is applied to study the light propagation inside the full-adder. Our numerical results demonstrate when the incoming light intensity increases, the nonlinear optical Kerr effect appears and controls the direction of light emitted inside the structure as desired. The maximum time delay and footprint of the proposed full-adder are about 3ps and 758.5 µm2, respectively. Therefore, due to the low time delay and small footprint, the presented design can be used as a basic mathematical operator in the all-optical arithmetic logic unit.

In this paper, we study a photonic crystal fiber (PCF) with circular lattice and engineer linear and nonlinear parameters by varying the diameter of air-holes. It helps us obtain low and high zero dispersion wavelengths in the visible and nearinfrared regions. We numerically demonstrate that by launching 100 fs input pulses of 1, 2, and 5 kW peak powers with center wavelength of 532 nm from an unamplified Ti:sapphire laser into a 100 mm length of the engineered PCF, supercontinua as wide as 290, 440 and 830 nm can be obtained, respectively. The spectral broadening is due to the combined action of self-phase modulation, stimulated Raman scattering and parametric four-wave-mixing generation of the pump pulses. The third and the widest spectrum covers the entire visible range and a part of near infrared region making it a suitable source for both white light applications and optical coherence tomography to measure retinal oxygen metabolic response to systemic oxygenation.

We propose an all-optical switch based on a microfibre Mach–Zehnder interferometer (MMZI) in which the MMZI is considered with a microfibre loop resonator (MLR) in one arm of it. The authors numerically demonstrate that the enhanced phase shift of the MLR near its resonance wavelengths can be used for constructive/destructive interference and switching functionality of the MMZI. The calculated switching threshold power of the switch is about 2 mW, which can be further reduced by the use of an MLR with more finesse, and the rising and falling times are computed with 21 and 91 ps, respectively. Natural connection to silica single mode fibres, easy configuration and high speed make it as a suitable choice for all-optical signal processing and communications applications.

In this paper, a square-lattice photonic crystal fiber based on optofluidic infiltration technique is proposed for supercontinuum generation. Using this approach, without nano-scale variation in the geometry of the photonic crystal fiber, ultra-flattened near zero dispersion centered about 1500 nm will be achieved. By choosing the suitable refractive index of the liquid to infiltrate into the air-holes of the fiber, the supercontinuum will be generated for 50 fs input optical pulse of 1550 nm central wavelength with 20 kW peak power. We numerically demonstrate that this approach allows one to obtain more than two-octave spanning of supercontinuum from 800 to 2000 nm. The spectral slicing of this spectrum has also been proposed as a simple way to create multi-wavelength optical sources for dense wavelength division multiplexing.

In this paper, we present various optical metamaterial nanoabsorbers with the aim of improving the refractive index sensitivity using the Fano response. The proposed absorbers consist of various parasitic elements such as single cross, broken cross, Jerusalem cross, and also single L and double L models. We numerically study their absorption and reflection using the three-dimensional finite-difference time-domain method and calculate the sensitivity and figure of merit (FOM) in every absorption peak (reflection dip). Our simulations reveal that the Fano resonance at longer wavelengths can be used for increasing the sensitivity and FOM. The proposed absorbers have been coated with an external material with a maximum thickness of 100 nm and refractive indices in the range of 1.05–1.2. We also study and compare the FOM for these structures. They are modified for 900 and 1200–1300 nm. The maximum FOM is achieved around 2400 RIU−1 for the double L nanoabsorber coated with 1.05 indexed material, while its sensitivity is 473 nm/RIU. This absorber is an appropriate component for the design of highly sensitive optical sensors.

Wise arrangement of antennas is critical in wireless cellular systems for both reductions of co-channel interference (CCI) and increase the quality of service (QoS). In this paper, a novel architecture for antenna arrangement in CDMA wireless cellular systems is presented. In this architecture that we called Microzone, every cell is divided into three (or more) zones and information transmission in downlink channel is done by an antenna which is placed at the outer region of the related zone. Also, the transmitting signal by the mobile station (MS) in uplink channel is received by all the antennas of the related cell. Analytical calculations of the received signal to noise ratio (SIR) and outage probability for both microzone and used architectures show that proposed architecture has better performance in compared with the used architecture. Also, simulation results confirm lower outage probability in uplink channel for microzone architecture.

In this article, we study the power control (PC) process in wireless cellular code division-multiple access systems under flat fading and propose a novel approach to find an optimum step size for closed-loop power control algorithms. In this approach, an optimum step size will be computed from a proposed function. This function depends on system parameters such as, the number of co-channel users, processing gain, the period of PC, Doppler frequency, channel attenuation and the order of diversity. Based on this computation, the mobile station (MS) adjusts its transmit power optimally to decrease interference for other co-channel users. Simulation results for different sets of system parameters show that the proposed algorithm decreases the bit error rate, the outage probability at the base station (BS), and increases the battery life of the MS compared with other values of the step size. The performance of the proposed algorithm is compared with the fixed-step-size power control algorithm and superiority of its performance is confirmed by simulation results. Moreover, the upper and lower bounds of the outage probability and the received signal-to-interference ratio for the proposed algorithm at the BS will be calculated.

Due to the large scientific and technical interest in the mid-infrared (MIR) spectral region, and the limitations of MIR light sources, we focus on the generation of a broad supercontinuum inside a short piece of As2Se3 microstructured optical fiber (MOF) with a square lattice. This is accomplished by filling the holes in the innermost ring of the proposed MOF with Ge33As12Se55 to produce ultraflat and near-zero dispersion. Simulations reveal that, by launching 100 fs input pulses centered at λ0=6.2 μm with a peak power of 2 kW into the MOF, an optical spectrum as wide as 9.5 μm will be achieved. This spectrum is a suitable source for MIR applications such as spectroscopy, food quality control, and gas sensing.