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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.

This paper proposes a novel design of plasmonic perovskite solar cell (PSC). It consists of an anti-reflective glass of fluorine-doped tin oxide (FTO), a compact buffer layer of n-type titanium dioxide (TiO2), an absorbing thin-film layer of perovskite (MAPbI3) integrated with gold (Au) nanospheres, a layer of p-type doped spiro-OMeTAD, and a layer of the cathode on aluminum (Al). This multilayer design’s primary purpose is to allow the light to enter the PSC with the minimum reflection and trap it in the active layer due to the presence of Au nanospheres. In this layer, the higher efficiency of PSC is achieved by localized surface plasmon resonances (LSPRs) in the wavelength range from 300 to 1100 nm. A reflective Al layer is used at the bottom of the device to reflect the light into the upper layers to considerably enhance the PSC absorption. The three-dimensional finite-difference time-domain method was conducted to find the best solution to Maxwell’s equations so that the best thickness and radius can be selected for each layer and Au nanospheres, respectively. Proper physical dimensions and Au nanospheres played a significant role in numerically indicating that the proposed structures are 60% more absorbent than the other conventional PSCs. In-house simulation software is used to approximate the solar cell by applying the finite element method to develop solutions for the drift–diffusion and Poisson’s equations. The examinations of the previous studies revealed that the current study is the first study that has simulated the real model of Auger recombination in perovskite. The results indicated that the proposed PSC embedded with Au nanospheres has the following properties: the built-in potential of 3.16 V, short-circuit current of 27.97 mA/cm2, the open-circuit voltage of 1 V, maximum power of 24.84 mW/cm2, fill-factor of 0.88, the conduction band of 3 eV, electron quasi-Fermi level of 2.5 eV, the hole quasi-Fermi level of 0.6 eV, and efficiency of 24.84%. Finally, the suggested PSC has performed 62% more efficient than conventional PSCs.

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 study investigated the optical limiting (OL) response of the dispersion of MoS2 nanosheets in N-methyl-2-pyrrolidone (NMP) which was made by liquid-phase exfoliation. We measured the OL response of different concentrations of the samples at two wavelengths of 405 nm and 532 nm using a continuous wave (CW) laser irradiation. It was observed that the value of the OL threshold changes by changing the laser wavelength and MoS2 concentration. To understand the mechanisms underlying these results, we use the spatial self-phase modulation (SSPM) and the Z-scan methods to measure the nonlinear absorption and refraction coefficients. It was revealed that the nonlinear absorption response is too weak. These findings highlight the significant role of the nonlinear refraction effect in the spatial self-phase modulation and the OL response of MoS2 dispersion under low-power laser irradiation.

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.

In this paper, we compare the characteristics of several waveguide Bragg gratings (WBGs) with sinusoidal and rectangular corrugated sidewalls in high confinement integrated optics. Our measurements confirm the performance of both the rectangular and sinusoidal grating as band-rejection filters for TE-polarized signals in the telecom C-band. These measurements demonstrate record high extinction ratios of 35 and 28.91 dB for sinusoidal and rectangular WBGs with a rejection bandwidth as narrow as 4.42 and 6.165 nm. The simulation results and measurements show that the filter bandwidth and coupling coefficient can be changed by altering the corrugation width ([Formula: see text]), allowing us to control the filter’s quality factor precisely. The bandwidth of rectangular WBGs drops for [Formula: see text] nm, constraining the design of devices requiring broadband WBGs. In contrast, the bandwidth of sinusoidal WBG continues to increase for [Formula: see text] nm, providing a wider bandwidth for designers. These findings demonstrate the potential for effective integration of new photonic functionalities into low-footprint electro-optical waveguide tools for sensing, communicating, and computing applications.

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.

This paper reports a new optical analog-to-digital converter (OADC) design based on nonlinear X-shaped photonic crystal ring resonators (X-PCRRs). The dielectric rods made of silicon and nonlinear rods composed of doped glass are used to form X-PCRRs. The proposed structure consists of a nonlinear three-channel demultiplexer and an optical encoder. The nonlinear demultiplexer converts the continuous input signal into three quantized discrete levels, and the optical encoder generates two-bit binary codes depending on the output channel number of the demultiplexer. 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-based structure, respectively. The wide TM photonic band gap of the fundamental PhC covers the second window of telecommunication in the C-band. Our calculations reveal that the proposed OADC has a maximum response time of about 4 ps and a sampling rate of 125 GS/s that is much faster than the designed ADC in previous studies. The proposed ADC also has a total footprint of 1785 μm2 with a minimum leakage loss.

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 report a new design of an all-optical filter using photonic crystal microstructure. Ring resonators, line defects, scatterer rods, microcavities, and coupling rods are used to form the filter in order to extract specific wavelengths at the output channels. The well-known plane wave expansion method is used to calculate the photonic band diagram. The widely used finite-difference time-domain method is also applied to study the light propagation inside the filter. Our numerical results demonstrate that the proposed structure has high transmission power, high-quality factor, and low cross-talk. They reveal an optical signal centered at 1522 nm exits the first output channel, which has an output-to-input ratio (OIR) of 95 % with a bandwidth (FWHM) of 0.4 nm, and an optical signal centered at 1520.8 nm exits the second output channel with an OIR of 98 % and an FWHM of 0.5 nm. The third output channel can exit the optical signal centered at 1518.2 nm with an OIR of 78 % and an FWHM of 0.4 nm. Furthermore, the fourth channel will exit the optical signal at 1519.3 nm with an OIR of 56 % and an FWHM of 0.4 nm. Therefore, the quality factors of the first to fourth outputs of the filter are equal to 3805, 3041, 3795, and 3798, respectively. The first to fourth outputs’ cross-talk values are also − 37 dB, − 36 dB, − 41 dB, and − 38 dB, respectively, which confirm the least interference between output channels. Besides, linear dielectric rods form the filter design that leads to the filter’s appropriate performance at a low input power that is the most important benefit of this work compared to other recently published articles. The maximum rise time of the proposed filter for all output ports is less than 8 ps. The structure also has ​​375.84 µm2, which makes the filter easy to use in photonic integrated circuits.

This paper reports a new design of a broadband absorber composed of graphene, dielectric, and gold layers. The designed absorber has four absorbent modes close to each other, which results in the formation of broadband absorption. The relative bandwidth, a key parameter to assess the bandwidth improvement, shows a significant increase in the proposed design compared to similar structures published in recent years. The numerical results also reveal this metamaterial absorber can be used for applications in the far-infrared frequency range due to choosing optimized dimensions and the graphene Fermi level. Unlike other graphene-based metamaterials, which require complicated structures to be able to attain broadband absorption, the physical structure of the proposed design has a relatively simple fabrication process. For further investigations, the effect of split geometry on the absorption spectrum is studied. Also, the use of graphene in this metamaterial absorber provides dynamic adjustability through electrostatic doping in order to tune the amount of absorption. This characteristic has been studied by changing the graphene Fermi level. This feature can be widely used in electro-absorption switches and modulators.

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.

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.

In this paper, we study fluid infiltration approach and rod filling technique for dispersion engineering of a photonic crystal fiber (PCF) composed of As2S3-Chalcogenide glass. The numerical results based on finite difference time domain method reveal that when air holes of the innermost ring in a PCF are infiltrated with suitable fluids or filled by glass rods, ultra-flattened near-zero dispersions with high nonlinearities will be achieved over a wide mid-IR wavelength range. The simulations demonstrate that when a 100 fs input optical pulse of 20 kW peak power and central wavelength of 2.5 μm is launched into a 10 mm length of the As2S3 PCF filled by PBG-08 rods, a ripple-free spectral broadening as wide as 9 μm from 1 to 10 μm can be obtained which is used as a suitable source for Mid-IR applications in molecular fingerprint region such as medical diagnosis of diseases, and drug detection.

In this paper, a triangular two-dimensional photonic crystal (PhC) of As2Se3-chalcogenide rods in air is presented and its photonic band diagram is calculated by plane wave method. In this structure, an optical waveguide is obtained by creating a line defect (eliminating rods) in diagonal direction of PhC. Numerical simulations based on finite difference time domain method show that when self-collimated beams undergo total internal reflection at the PhC-air interface, a total reflection of 90° occurs for the output beams. We also demonstrate that by decreasing the radius of As2Se3-chalcogenide instead of eliminating a diagonal line, a two-channel optical splitter will be designed. In this case, incoming self-collimated beams can be divided into the reflected and transmitted beams with arbitrary power ratio by adjusting the value of their radii. Based on these results, we propose a four-channel optical splitter using four line defects. The power ratio among output channels can be controlled systematically by varying the radius of rods in the line defects. We also demonstrate that by launching two optical sources with the same intensity and 90° phase difference from both perpendicular faces of the PhC, two logic OR and XOR gates will be achieved at the output channels. These optical devices have some applications in photonic integrated circuits for controlling and steering (managing) the light as desired.

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.

Supercontinuum (SC) in visible and near-infrared regions is used as a source for optical coherence tomography (OCT) method to measure vascular oxygen saturation in retinal and choroidal circulations. To generate SC in these regions, we first study magnesium fluoride (MgF 2 ) solid core photonic crystal fibers (PCFs) with submicron air-holes. Then by varying the air-holes diameter we engineer the dispersion and nonlinear parameters as desired. We demonstrate by launching input pulses with center wavelengths of 532 and 640 nm into an engineered PCF, supercontinua as wide as 530 and 580 nm can be obtained that cover the entire visible range and a part of near infrared region making it a suitable source for both white-light and OCT applications.

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.

In this paper, we propose a novel design of a tunable electro-optic analog-to-digital converter. The proposed structure consists of a tunable three-channel demultiplexer and an optical encoder. The first part provides sampling and quantization of the input electrical analog signal based on the applied potential to the graphene nanoshells (GNSs), while the second part converts the quantized levels into two-bit binary code. The electro-optic demultiplexer is realized using three GNS-based photonic crystal resonant cavities and can be tuned by applying different biasing of the gate voltage to the GNSs. For appropriate chemical potential values of GNS, each resonant cavity can drop the optical beam into its corresponding output port. This tunable ultrafast device supports a maximum sampling rate of up to 222 GS/s, whereas its compact footprint is about 692 µ m 2 . The proposed device opens a new window to the design and fabrication of tunable graphene-based photonic crystal circuits to develop electro-optic on-chip processing systems.

In this paper, linear and nonlinear properties of photonic crystal fiber (PCF) are studied in terms of wavelength for triangular and square lattices to investigate the effects of changing the fiber dimensions including air-hole diameter, pitch size and the number of air-hole rings on the dispersion profile and its nonlinear parameter. A chalcogenide based PCF is proposed in this paper and modeled in TCAD environment of Mode Solution software related to Lumerical package. The finite difference eigenmode solver numerical method is utilized in the modeling and anisotropic perfectly matched layers (PML) are assumed as absorbing boundaries to be positioned outside the outer-most ring of the air-holes. Accordingly, the effects of changing each of aforementioned parameters on the value and slope of dispersion and loss profiles as well as on its nonlinear parameter are systematically determined. For instance, numerical results achieved by the simulation results show that both the value and slope of dispersion profile are reduced by considering the diameter of air holes with a constant value and increasing the pitch size of the fiber. Moreover, considering a fixed value for the pitch size and increasing the air hole diameters lead to an increase of dispersion profile in terms of wavelength. Additionally, the numerical results show that an increase in the diameter of the air holes results in an increase in the nonlinear parameter. Further, the input source’s wavelength increase will result in the reduction of the nonlinear parameter.

Due to the pronounced scientific and technical attention paid to the mid-infrared spectral region, we focus on ultra-wide mid-infrared supercontinuum generation in As40Se60 chalcogenide SIF and PCF—step index and photonic crystal fibers—using a symmetrized split step Fourier method (S-SSFM). Simulations reveal, in response to launching 100 fs input pulses of 50 kW peak powers, with near zero dispersion wavelengths centered about $\lambda _{0} = 8.5$ μm, into 50-mm long As40Se60 SIF and solid core PCF, 8.5 and 11-μm supercontinua can be achieved, respectively. Moreover, numerical results also show, when ultra-short pulses of center wavelengths $\lambda _{0} = 12$ μm are launched into those SIF and PCF, ripple free spectra as wide as 10 and 13 μm can be attained, respectively. These spectra are useful for safe spectroscopic medical imaging diagnosis such as early cancer diagnostics, and other spectroscopic applications such as gas sensing and food quality control.

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.

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.

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.

In this paper, femtosecond optical pulses compression and supercontinuum generation in a triangular silicon photonic crystal fiber at 2500 nm are investigated. A region of large minimum anomalous group velocity dispersion, negligible higher order dispersions and unique nonlinearity of silicon are used to demonstrate compression of 100 fs initial input optical pulses to 2.5 fs and ultra-broadband supercontinuum generation with very low input pulse energy over short distances of the fiber.

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.

We propose a technique based on optofluidic infiltration to design a photonic crystal fiber (PCF) to control chromatic dispersion for supercontinuum generation. Selectively infiltrating the PCF air-holes with an optical fluid having an appropriate refractive index, we have achieved a PCF with low confinement loss and ultra-flattened near zero dispersion centered about λZD ~ 1325 nm, without a need for nano-scale geometrical tuning. Numerical simulations show that femto-second pulses, with center wavelengths within the range of 1250 nm ≤ λ0 ≤ 1625 nm, can generate relatively flat supercontinuum spectra as wide as 640 to 1180 nm, passing through a 250-mm long PCF whose dispersion profile is engineered via selective optofluidic infiltration. Simulations also show that optical fluid with refractive index of nF = 1.32 for input signals having the aforementioned range of wavelengths result in the widest flat supercontinua. This is attributed to the smallest corresponding effective mode area as well as the smallest and flat corresponding dispersion both of which enhance the PCF nonlinearities.

In this paper, the effects of physical parameters on the performance of unbalanced Mach–Zehnder interferometers (MZIs) are numerically studied by solving Maxwell's equations on a cross-section of the waveguide using finite-difference eigenmode method. The MZIs are fabricated by the electron beam lithography with a single etch process on a silicon-on-insulator wafer. The transmission profiles and free spectral ranges (FSRs) of the fabricated MZIs are also measured using a custom-built automated measurement setup and compared with the simulation results of Corner analysis and Monte-Carlo analysis methods. Our comparison reveals that the measured FSRs of the fabricated MZIs are in the range determined by the Monte-Carlo analysis. While all measured FSRs are less than the FSRs indicated by the Corner analysis. Therefore, Monte-Carlo analysis can be used as an accurate numerical method for the study of photonic integrated circuits before fabrication.

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.

We numerically report super-flat coherent mid-infrared supercontinuum (MIR-SC) generation in a chalcogenide Assub38.8/subSesub61.2/subphotonic crystal fiber (PCF). The dispersion and nonlinear parameters of Assub38.8/subSesub61.2/subchalcogenide PCFs by varying the diameter of the air holes are engineered to obtain all-normal dispersion (ANDi) with high nonlinearities. We show that launching low-energy 50 fs optical pulses with 0.88 kW peak power (corresponding to pulse energy of 0.05 nJ) at a central wavelength of 3.7 μm into a 5 cm long ANDi-PCF generates a flat-top coherent MIR-SC spanning from 2900 to 4575 nm with a high spectral flatness of 3 dB. This ultra-wide and flattened spectrum has excellent stability and coherence properties that can be used for MIR applications such as medical diagnosis of diseases, atmospheric pollution monitoring, and drug detection.