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A multiple quantum well (MQW) transistor vertical-cavity surface- emitting laser (T-VCSEL) is designed and numerically modeled. The impor- tant physical models and parameters are discussed and validated by modeling a conventional VCSEL and comparing the results with the experiment. The quantum capture/escape process is simulated using the quantum-trap model and shows a signicant eect on the electrical output of the T-VCSEL. The parameters extracted from the numerical simulation are imported into the an- alytic modeling to predict the frequency response and simulate the large-signal modulation up to 40 Gbps.

A transparent, flexible graphene field effect transistor (GFET) based on ferroelectric gate is demonstrated. In this device, the single layer graphene was fabricated by chemical vapor deposition method, and transferred to the polyethylene terephthalate substrate. Then the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric polymer layer film was used as the gate dielectric for the graphene FET. Based on the P(VDF-TrFE)/graphene heterojunction FET, Hall Bar structure was fabricated. The transport properties of the graphene channel at low temperature and retention characteristics at different temperature are investigated in detail. These special properties indicated that the GFET might be useful for many particular applications, such as a non-volatile memories, flexible electronic devices and phototransistors.

The spatial self-phase modulation effect in graphene oxide with silver and gold nanoparticles were considered for demonstration of nonlinear properties of nanocomposites. Gold and silver nanoparticles were fabricated in graphene oxide using laser ablation at different times. The prepared samples were characterized using UV–Visible, transmission electron microscopy and X-ray diffraction spectroscopy. The absorption peaks in blue and green ranges were appeared related to silver and gold nanoparticles, and the nanoparticles were capped by graphene oxide in a spherical shape. The concentration of nanoparticles increased with an increased the ablation time. The nonlinear effect in graphene oxide and graphene oxide with gold and silver nanoparticles was then observed using the spatial self-phase modulation technique at 532 and 405 nm wavelength. Consequently, the self-defocusing effect was appeared in the mentioned medium, and the number of spatial self-phase modulation rings increased with an increased volume fraction of nanoparticles.

The graphene and graphene oxide sheets were prepared from directly exfoliated and Hummer’s method. Nitrogen doping was applied with the assistance of ultra-sonicator to achieve doping via a simple, low-cost aqueous route. The size of graphene and graphene oxide sheets was examined by transmission electron microscopy with a size of several micrometer. The doping phenomenon was achieved by the addition of aqua ammonia and the analysis were examined by Raman microscopy. The approve of N-doping was got with the appearance of G′ band. The existence of nitrogen element were further examined by energy dispersive spectroscopy.

This paper investigates and enhances unmanned aerial vehicle (UAV) relay-assisted free-space optics (FSO) optical wireless communication (OWC) systems under the effects of pointing errors (PEs) and atmospheric turbulences (ATs). The incorporation of UAVs as buffer-aided moving relays in the conventional FSO (CFSO) relay-assisted systems is proposed for enhancing the performance of PEs through AT. Using M-PSK (phase shift keying) and M-QAM (quadrature amplitude modulation), the impact of PEs on transmission quality is evaluated in this work. We evaluate and optimize the symbol error rate, outage probability (OP), and signal-to-noise ratio (SNR) for the UAV-to-ground station-based FSO communications systems. The spatial diversity-based relay-assisted CFSO systems can enhance the performance of the UAV-UAV FSO links. In this paper, a new FSO (NFSO) channel model for the hovering UAV-FSO OWC fluctuations under the PEs, AT effects, jitter, deviation, receiving an error, and wind resistance effects are established. To improve the performance of hovering UAV-based FSO relay OWC systems. We reduce the influence of UAV-FSO OWC fluctuations under PEs and AT effects. By receiving incoherent signals at various locations, the spatial diversity-based relay-assisted NFSO systems can significantly increase the system's redundancy and enhance connection stability. Numerical results show that to achieve a bit-error-rate (BER) of $$\le 10^{ - 5}$$ ≤ 10 - 5 , the required SNR is ≥ 23 dB when the wind variance of the UAVs $$\sigma_{\alpha }^{2}$$ σ α 2 increases from 0 to 7 mrad with FSO link distance L = 2000 m. The required SNR is ≥ 25 dB when the wind variance $$\sigma_{\alpha }^{2}$$ σ α 2 is 1 mrad at an OP of $$10^{ - 6}$$ 10 - 6 . To obtain an average BER of $$10^{ - 6}$$ 10 - 6 , the SNR should be 16.23 dB, 17.64 dB, and 21.45 dB when $$\sigma_{\alpha }^{2}$$ σ α 2 is 0 mrad, 1 mrad, and 2 mrad, respectively. Using 8-PSK modulation without PEs requires 23.5 dB at BER of $$10^{ - 8}$$ 10 - 8 while 16-QAM without PEs requires 26.5 dB to maintain the same BER of $$10^{ - 8}$$ 10 - 8 . Compared with 16-QAM without PEs, the SNR gain of 8-PSK without PEs is 3 dB. The results show the relay-assisted UAV-FSO system with five stationary relays can achieve BER $$10^{ - 8}$$ 10 - 8 at 25 dB SNR in the ideal case and $$10^{ - 5}$$ 10 - 5 at 27 dB SNR with AT and PE at FSO length 1000 m. The results show the relay UAV-FSO system outperforms the CFSO at the BER and SNR performance. The effects of UAV’FSO s fluctuation increase when the UAV-FSO link length, $${\text{L}}_{{{\text{fso}}}}$$ L fso increases. The results of the weak turbulence achieve better SER compared with MT and ST. The obtained results show that decreasing $${\text{L}}_{{{\text{fso}}}}$$ L fso can compensate for the effects of UAV-FSO link fluctuation on the proposed system. Finally, we investigated the CFSO relay-assisted UAV-FSO system with aided NFSO-UAVs spatial diversity-based relay-based on NFSO OWC and revealed the benefits of the resulting hybrid architecture.

In this paper, we suppose an underwater optical wireless communication (UOWC) system, where the communication utilizes visible light communication for its advantages as wide spectrum, high data rate and high accuracy. The novelty of this paper is focused on improving the channel estimation between transmitter and receiver, where using Kalman Filter (KF) for channel estimation in UOWCs achieves the best results as compared to other traditional channel estimation methods. The scenario of this paper is summarized in transmitting data from transmitter to receiver via underwater harbor and coastal channels. Two channel models are utilized: weighted double gamma functions (WDGF) and a combination of exponential and arbitrary power function (CEAPF). The modulation technique used is optical orthogonal frequency division multiplexing with two kinds: direct current optical orthogonal frequency division multiplexing (DCO-OFDM) and asymmetrically clipping optical orthogonal frequency division multiplexing (ACO-OFDM). Three different techniques are used for channel estimation: Least Square (LS), minimum mean square error (MMSE), and KF. The simulation results reveal that the ACO-OFDM modulation technique with CEAPF channel modeling using KF achieves the lowest bit error rate (BER) compared to other channel estimation methods. The improvement percentage at BER = 10−1 is 13.3% for ACO-OFDM over DCO-OFDM with CEAPF in coastal water and is is 9.3% for WDGF. This indicates that CEAPF performs about 4% better than WDGF for ACO-OFDM than DCO-OFDM in terms of channel estimation.

This paper aims to improve the channel estimation (CE) in the indoor visible light communication system. The proposal of this paper deals with a system that depends on a comparison between Deep Neural Network (DNN), Yolo v3, and Kalman filter (KF) algorithm, for two optical modulation techniques; asymmetrically clipped optical-orthogonal frequency-division multiplexing (ACO-OFDM) and direct current optical-orthogonal frequency division multiplexing (DCO-OFDM). The CE can be evaluated by the error rates in the received bits, where increased error means a performance decrease of the system and vice versa. Receiving less errors at the receiver indicates improved CE and system performance. Hence, the main aim of our work is to decrease the error rate by using different estimators. Furthermore, we apply automatic hyper-parameter approach and Bayesian optimization, to Yolo v3 model to improve the system performance and reduce the positioning error. The metric parameter of bit error rate (BER) aims to determine the improvement ratio in different systems. The model in this paper is based on training with OFDM samples of signal with labels which are received and are corresponding to the signals of OFDM. At a BER = 10−3 with DCO-OFDM, the DNN outperforms KF with 1.7 dB (8.09%) at the bit energy per noise $$(E_{b} {/}N_{o} )$$ ( E b / N o ) axis. Also, for ACO-OFDM at BER = 10−3, the DNN achieves better results than KF by about 1.9 dB (11.8%) at the $$(E_{b} {/}N_{o} ){ }$$ ( E b / N o ) axis. For different values of M in QAM, the DNN outperforms KF for ACO-OFDM by average improvement of ~ 1.2 dB (~ 13%).

In this paper, core-shell nanoparticles are used to provide a transparent high-quality display. To realize this idea, Si-SiO2 core-shell nanoparticles have been used to achieve the most suitable nanoparticle composition for a transparent color display with high transparency and contrast. For color transparent monitor the superimposed QDs are used. There is a basic question for the realization of the proposed transparent monitor. What is the ratio of nanoparticles (ratio of three QDs) for three colors in the proposed monitor? In this paper, we are going to acknowledge this question. As it is clear, the scattering peaks for red, green, and blue are different because of the physics of the scattering that is wavelength-dependent. Thus, the optimum ratio for each color should be obtained. The numerical method of Finite-Difference Time-Domain is used to simulate and calculate the optical properties of the proposed transparent monitor. The effect of different combinations of nanoparticles to have the maximum dispersion at blue, green, and red wavelengths and the minimum absorption at other wavelengths has been investigated. Finally, the optimum ratio and arrangement of nanoparticles for all colors are reported and numerically evaluated.

In the field of medical thermotherapy, heating cancer cells to 42.5–43 °C by microwave can make cancer cells inactive. Beyond this temperature range, normal cells are also damaged, which makes the accuracy of temperature detection very important. The active temperature sensor is seriously disturbed by strong electromagnetic field, which is difficult to meet the temperature measurement requirements in the field of microwave hyperthermia. Therefore, the fluorescent optical fiber temperature sensor has been applied in this field due to its insulation advantages. In order to improve the accuracy of the fluorescent optical fiber temperature sensor, a new weighted integral ratio algorithm is implemented in this paper. The numerical simulation show that the algorithm is completely unaffected by the DC bias in the system. In addition, the influence of random noise is greatly suppressed by integral processing and weighting processing. In this paper, the high-precision fluorescent optical fiber temperature sensor is realized by establishing the optical path, circuit and data processing algorithm of the system. The system is tested at 16 to 100 °C. The test results show that compared with the two-point method and the integral ratio method, the standard deviation of the weighted integral ratio algorithm is reduced by 67% and 50%, respective. The standard deviation of this algorithm is about 0.1°C. In addition, the response time of the algorithm is reduced by about 4 times. In summary, this algorithm can solve the problems of low accuracy, poor stability and long response time caused by data processing algorithms in the system.

In this paper, we present the analytic and numerical solutions of the newly modified Zakharov–Kuznetsov equation. This model is used to study the waves in different plasmas. The analytical solutions were achieved by the extended tanh method and the Sine Gordon method while the numerical one is achieved by the implicit finite difference method and the local truncation error and the stability analysis for the difference scheme are given. Graphical representations of exact and numerical solutions are given to illustrate our results. In addition to the other known results in the literature, the paper contributes new analytical and numerical results.

This paper explores the numerical analysis of a highly performed SPR biosensor employing a hybrid structure of Bismuth Ferrite-Bromide materials-BP/Graphene. In the study, we have considered several bromide materials, such as rubidium bromide (RbBr), potassium bromide (KBr), sodium bromide (NaBr), caesium bromide (CsBr), lithium bromide (LiBr), silver bromide (AgBr) and thallium bromide (TIBr). The investigation is executed at 633 nm wavelength using the transfer matrix method and angular interrogation technique. Firstly, different refractive index prisms have been discussed, and it has been discovered that utilizing a low refractive index prism can improve sensitivity. Furthermore, the performance of the proposed SPR sensor is investigated and observed that BP-based structure (Bismuth Ferrite-bromide materials-BP) facilitates better SPR performance than the graphene-based structure (Bismuth Ferrite-bromide materials-graphene). The highest performance parameters, such as S of 468 deg/RIU, quality-factor of 87.80RIU−1, figure-of-merit of 87.79, and detection-accuracy of 0.44 are achieved for BP-based structure (Bismuth Ferrite-TIBr-BP), which are 1.32, 1.46, 1.51, and 1.47 times higher than the respective performance of the graphene-based structure. In addition, resonance-angle-shift variations versus a unit of sensing RI changes are observed in this paper.

The increasing availability of unmanned aerial vehicles (UAVs) is an exciting part of future emerging technology with advanced scientific and industrial interests. Free space optical (FSO) communications’ ability to offer very high data rates and the mobility of unmanned aerial vehicle (UAV) flying platforms make the delivery of Fifth-Generation (5G) wireless networking services appealing to FSO-UAV-based solutions. UAVs play a greater role in end-to-end delivery in next- generation wireless networking systems, serving as a base station, capacity enhancement, high data access, and other disaster management systems. To establish a link between unmanned aerial vehicles and ground stations, FSO can be applied. But, the different weather conditions liken rain, fog effects on the performance of the FSO link, contributing to the loss of the signal. In this paper, we proposed polarization shift keying (POLSK) modulated FSO link based UAV–UAV communication system for 6G beyond applications. We examine the effect of different weather conditions such as rain, fog on the bit error rate (BER) performance of the proposed system. Novel closed-form expressions for UAV–UAV based FSO propagation channel are derived, and BER performance is investigated under different weather conditions. Fog and rain are the main limiting factors mitigated in this paper by suitable mitigation techniques by increasing receiver field of view.

Visible Light Communication is determined to be as a new technology for recent wireless digital communications. This paper makes the description over an innovative VLC system with superior performance and efficiency over previous systems. In this paper, Indoor VLC communication model is being proposed in Single Input Single Output (SISO) and Multiple Input Multiple Output (MIMO) using Enhanced Optical Orthogonal Frequency Division Multiplexing (EO-OFDM). The MIMO VLC system overcomes the limitations of channel capacity caused by the limited LED modulation bandwidth using the parameter of high Signal to Noise Ratio (SNR) of the SISO channel LED lighting requirements. This article enumerates the comparison over the Enhanced Optical OFDM (EO-OFDM), which is being utilized as an enhanced-bandwidth technique, with the conventional Generalized Frequency Division Multiplexing (GFDM), Space Time Block Coded OFDM (STBC-OFDM), Optical OFDM. The proposed system enhances the Bit Error Rate (BER) performance, throughput for all possible channel gains of MIMO over SISO VLC communication compared to other conventional systems. Inspite of maintaining the same data transmission rate as the conventional method, the Bit Error Rate (BER) of the proposed system has been improved by 10–5 at SNR equal to 20 dB. Based on the acquired results, EO-OFDM has provided higher data rates than OFDM on channels with limited frequency bands and makes the reduction over the Peak Average Power Ratio (PAPR). In the proposed EO-OFDM technique, the performance analysis of throughput over SNR has been computed in comparison with O-OFDM, OAK-OFDM, PWM-OFDM with which the throughput of 20 Mbits per second has been achieved. Added to that the maximum throughput of 7.6 Mbits per second has been achieved for the proposed EO-OFDM technique which is very high than O-OFDM, OAK-OFDM and STBC-OFDM in the MIMO technique.Whereas, under the constraints of non-linear characteristics of LED and limited dynamic range, the overall performance of this experimentation is better than other than state of art techniques.

A key area of wireless communications is visible light communication which uses solid-state light-emitting-diode. This paper shows, a comparative study to optimize the received signal strength indication (RSSI) in the optical wireless link between two optimization algorithms. The optimization algorithm we used in the paper is a genetic algorithm (GA) and a particle swarm optimization (PSO) algorithm. To, compute the maximum RSSI over the non-line-of-sight (NLOS) link, within an indoor environment, and to find the optimum NLOS route through distinct angles to achieve better communication quality, we have used those algorithms. Simulations were performed at matlab to check the feasibility of the scheme proposed. Also, we have compared the efficiency of the both system. In addition, GA and PSO detect the maximum RSSI of the receiver (Rx) in a specific direction instead of calculating RSSI at any random angle. The simulation result shows that the proposed system precisely detects the direction that provides an optimal RSSI for the Rx. This paper concludes that the GA is computationally effective while compared with PSO. After several iterations, the result estimates that the average elapsed time of the GA is 0.21 ms and the PSO is 30 ms, respectively. In the case of user positions 1 and 2, the percentage enhancement for GA as compared to PSO is almost 4.2% and 12.5% respectively.

Multi band solar cells provide the possibility to achieve ultra-high power conversion efficiency by absorbing incident infrared wavelengths. In this paper, we provide theoretical evaluation and framework for maximum power conversion efficiency limit for multiband solar cells. In order to achieve this goal, the genetic algorithm (GA) optimization techniques are used. To precise calculation, solar cells with three and four intermediate bands are considered in detail in this paper. Our calculation shows the maximum efficiency of 62.9% and 70.3% for the three and four band solar cells, respectively. The development of this algorithm lets us design and propose a novel and appropriate materials for photovoltaic structures to achieve maximum power conversion efficiency. It should mention that the proposed method can open a new research field in the synthesis of new materials to realize the proposed idea.

The present paper examines a photonic crystal-based ring resonator created using a triangular lattice to design a biosensor with a sensing cavity based on an optical filter. Using this structure, the central wavelength of 1547 nm can be filtered with a transmission coefficient of 95%. Additionally, the maximum value of ultra-high-quality factor (Q) in the proposed structure is about 3740 at 1496 nm wavelengths. Moreover, the minimum detection limit and maximum sensitivity for the proposed structure are calculated to be 7.15 × 10–8 RIU (refractive index unit) and 561 nm/RIU, respectively. In this paper, the effects of structural parameters, including refractive index, lattice constant, and the radius of the rods in the resonator core on the central wavelength of the filter, transmission coefficient, and quality factor have been investigated. The plane wave expansion (PWE) method has been used to extract the photonic bandgap and the finite-difference time-domain (FDTD) method has been used to study the optical behavior of the photonic crystal structure.

Orthogonal frequency division multiplexing (OFDM) of the optical communication system is a known approach for light fidelity and the screen-to-a-camera (S2C) communication system is an innovative implementation for optical camera communication (OCC). In This paper, two dimensional (2D) asymmetrically clipping optical (ACO) OFDM for the S2C model can be obtained which develops a single screen display, consisting of several cells, for a data rate of up to 100 kb/s. This paper contains an innovative system design focused on validation of implementation and theoretical study. The source distribution of the ACO OFDM system has been implemented using LAB VIEW software. The performance of the suggested model was verified through numerical assessment techniques, as it was checked that within the transmission distance of 4.5 m and the field of view of 30 $$^\circ$$ overall bit error rate (BER) of 10−6 and signal to noise ratio (SNR) 18 dB is achieved. Under the existing IEEE 802.15.7 m standard, the overall results of the S2C OFDM system are being evaluated by comparing them to the 2D OFDM OCC system to illustrate the efficiency of the proposed scheme.

In this paper, jitter modulation of SPADs in different photon wavelengths is explored. It is shown that in p+/n-well, or p+/deep n-well SPADs the jitter increases with increasing the photon wavelength, due to an increase in avalanche buildup time (τ). The avalanche buildup time is enhanced in higher wavelength due to the deeper photon absorption depth, and lower avalanche probability in deeper depths in p+/n-well or p+/deep n-well structures, which itself enhances the SPAD jitter. The finding of this paper could successfully describe the two previously implemented SPAD jitter measurement results.

Quantum key distribution uses the principle of quantum physics to realize unconditionally secure key distribution protocol. But this kind of security needs to be based on the authenticated classical channel. Although there are quantum key distribution protocols without classical channel, authentication is still needed. In the process of key distribution, authentication is not considered, which is also a problem of quantum key distribution protocol. In this paper, a quantum key distribution protocol with two-way authentication is proposed. Identity authentication is carried out at the same time of key distribution. If the identity authentication fails, the key distribution protocol cannot be carried out. If the key distribution protocol is aborted, the identity authentication is not successful. The conclusion of this paper is based on a central authentication system supported by symmetric encryption theory, which uses pseudo-random functions, multiple sets of quantum conjugate bases and Measurement-device-independent technology to simultaneously achieve two-way authentication and key distribution.

The increasing demand for bandwidth through modern applications and multimedia services has led to high-speed wireless communications. Optical wireless communications (OWC) encourages solutions that provide a higher data rate due to the large bandwidth available. In this paper, performance enhancement approaches are studied and simulated for visible light communication (VLC) as a case study. The orthogonal frequency division multiplexing (OFDM) systems are used to investigate Intensity modulation/direct detection (IM/DD) to improve the performance of VLC. The IM/DD in OWC requires positive real OFDM symbols, so there are many approaches to satisfy this requirement. This paper proposes a model of Asymmetrically Clipped DC-Biased Optical (ADO-OFDM) to use in OWC/VLC environment. The proposed system has avoided the use of the noise cancellation technology that is used in traditional ADO-OFDM. The results show that the ADO-OFDM has the best spectral efficiency than DC-biased optical (DCO-OFDM) and Asymmetrically clipped optical (ACO-OFDM). Also, it has better optical efficiency than DCO-OFDM with the equally overall bit error rate (BER) at the same signal-to-noise ratio. Hamming channel coding/decoding with different code lengths is applied in various optical OFDM schemes for BER improvements. Furthermore, we simulate and analyze these optical OFDM systems with many modulation orders.

The paper describes design and analysis of Tera Hertz Optical Asymmetric Demultiplexer (TOAD) switch using quantum dot semiconductor optical amplifier (QDSOA) and all- optical digital to analog converter (DAC). The QDSOA based TOAD or QDSTOAD and the DAC performance optimization for control power variations shows that 1.5 mW pump or control power gives the optimized performance as far as the extinction ratio is concerned for the TOAD. At the same power absolute error (e) and dynamic range for DAC also shows maximum. The present paper investigates relative output, absolute error and dynamic range for the performance analysis of the DAC. An absolute error as low as 0.25% and dynamic range (11.765 dB) very close to the ideal value (11.761 dB) ensures effectiveness of these devices. These devices show immunity to the amplified spontaneous emission noise.

Reduction in the dimensions of silicon based devices has produced extraordinary developments in the performance of electronic systems. Recently, the advantages and challenges that caused by silicon devices shrinking have been investigated in many studies. Most of them have concluded that silicon technology is coming to an end and new innovations are required in the near future. Graphene is the promising candidate material as building blocks for nanoelectronic industry in order to silicon technology replacement. Graphene is first two dimensional materials that has significant potential in future nanoelectronic devices and other nanotechnology applications; therefore, it is an attractive subject for the researchers and scientists. Graphene is a carbon allotrope and is the basic element of other carbon allotropes. In this paper, main graphene production approaches are mentioned. The mechanical, thermal, optical, electrical, electronic and other fundamental properties of graphene are introduced. Moreover, it is considered as a novel material with numerous applications, which, we mention a few of important utilizations of graphene and its derivatives. Then, the different types of defects in graphene and their specifications, the methods of defect generation, defect healing, and properties of defective graphene are studied. Graphene nanoribbons and their geometric structures, fabrication approaches and electronic specifications are investigated. The effects of width, vacancy defect and doping concentration on the band structure of the graphene nanoribbons are extracted with ATK software in this paper. Simulation results showed that by increasing in the width, vacancy defect and doping concentration of nanoribbons, their band gap were decreased. These properties are suitable for controlling the channel of graphene nanoribbon field effect transistors.

Quantum well infrared detector has been extensively applied in military and civil fields. In order to break through the bottleneck of low quantum efficiency, a novel quantum well infrared photodetector based on SiO2–dielectric–metal microstructure has been proposed and investigated in this paper. The detector is composed of three layers, which are SiO2 particle array on the top, quantum well in the middle layer and metallic film at the bottom. The results shown that the SiO2–dielectric–metal sandwich structure can absorb electromagnetic waves between 14 and 15 µm which the quantum well infrared photodetector work at. In addition, we have studied the influence of the parameters of the detector structure, it is found that the absorption band is insensitive to period of photodetector microstructure and the thickness of SiO2 layer, which indicates the quantum well infrared photodetector has a stable performance. The quantum well infrared detector proposed in this paper has large potential applications in the miniaturization and integration of optoelectronic devices in the future.

In this paper, a new model of multi-layer metamaterial perfect absorber (MPA) in the terahertz region has been introduced. This model is similar to the classic absorber model, ie the three traditional layers of metal-dielectric-metal. The difference is that the middle layer has changed in height and consists of 3 separate layers with the same material. Therefore, the middle layer of the proposed structure is metamaterial. Numerical results of the simulation show that the absorption rate of the perfect absorber at 6.86 THz is 99.99%. Also, by changing the width of the two middle layer columns w, a dual-band perfect absorber with an average absorption rate of 97.18% is obtained at frequencies of 4.24 THz and 6.86 THz. A significant advantage of this paper over other works is that this absorber is adjustable, in addition to obtaining a nearly perfect dual-band absorber with a narrow-band peak by adjusting the parameters and also a nearly broad-band absorber can also be obtained by changing the parameters without re-manufacturing the structure. We believe that the proposed absorber has potential in filtering, detection and imaging.

Visible Light Communication (VLC), which gives communication alongside illumination, has increased a great deal of enthusiasm amongst researchers. VLC system needs to consider dimming control to offer effective communication while illuminating. In this paper, a dimming control scheme based on pulse position modulaton (PPM) and inverse PPM is proposed, which supports different dimming levels. PPM supports low dimming value whereas inverse-PPM has an inherent property of supporting higher dimming value for the same block length. Hence, the proposed scheme utilizes both PPM and inverse-PPM to achieve different dimming target values. This paper presents the algorithm for encoding and decoding of multi-header hybrid pulse position modulation (MH-HPPM) scheme and also shows the NI Labview SubVI code for generating the MH-HPPM frame under dimming values of 0.25, 0.33, 0.5, 0.67 and 0.75. Simulations are executed in MATLAB 2017a to simulate random input bits using the proposed scheme in the VLC system for different dimming values and evaluate the BER performance of the scheme. The simulation result shows that the proposed scheme performs better for dimming value $$\alpha = 0.25$$ , block length $$K = 4$$ , is bandwidth efficient and hence can be considered as an alternate dimming control scheme.

This paper introduces a fractal model of the Radhakrishnan–Kundu–Lakshmanan (RKL) occurring in a fascinating physical phenomenon in birefringent fibers. He's variational approach is used to identify novel fractal RKL-equation optical soliton solutions. The required novel criteria to ensure the existence of appropriate solitons are provided. The three-dimensional surfaces of the recording solutions are demonstrated by specifying a variety of suitable parameter values. The focus of this paper is on the groundbreaking RKL-equation work frontiers and other associated nonlinear evolution models in the field of optical solitons and solitary waves.

In the complex background of information warfare, we often encounter multiple air defense radars or multi-band radars and carry out effective jamming against them simultaneously. Due to that radar always works at different frequencies, we need to generate jamming signals with sufficient bandwidth, covering all frequencies of radar and aiming at each band at the same time for jamming, which is called multi-point targeting jamming. In this paper, using two coherent optical frequency combs through the Vernier caliper effect with frequency “dislocation” is proposed, and produce multiple stable central frequencies through beat frequency. This scheme can realize widely tunable frequency bands. And this paper implemented maximum tunable range of 1.1–23.4 GHz with 100 MHz bandwidth.

Improvement of visible light communication (VLC) technology and the presence of the illumination encouraged the researches to research in VLC-based indoor positioning. Recently, researchers published several papers on VLC based localization systems, however there are not a lot of survey papers in this issue. In this paper, a deep analysis survey of VLC based localization systems is introduced. Researches from pioneering papers to the state-of-the-art in the field of VLC based position are analyzed and classified based on the localization techniques, types of transmitters and receivers, and multiplexing techniques. Different from other surveys, we analyze the accuracy of VLC based localization system in the practical and simulation environments.

Entanglement transmission is utilized widely in quantum communication. In this paper we establish a model, which characterizes the performance of entanglement state passing through the composite free space channel. This free space channel is compounded with atmosphere, sea surface and underwater channel. Based on the model, the entanglement photon pairs transmitted through composite channel are simulated. Simulation results show that the beam wandering, the incident angle of the beam on the sea surface, the concentration of chlorophyll in the seawater and other factors will lead to the degradation of the entanglement and these factors have a nonlinear relationship with transmittance. Moreover, the increase of the chlorophyll concentration is found to be a relatively heavy impact on the entanglement. In addition, expanding the aperture size of the receiving telescope will improve entanglement. The research of this paper has momentous meaning to the transmission of quantum entanglement in free space. What’s more, the results have an extremely vital reference value for quantum communications in diverse natural environments.

Accurate and efficient monitoring of electrical machine (EM) operating parameters, including temperature, mechanical vibration, torque and rotating speed and others that can indicate the EM health conditions is becoming ever more important in the world of electrical drives. The traditional methodology of one sensor per parameter can be theoretically replaced by a “one sensor measures all” technology, which can be achieved through the use of fibre-optic sensors (FOS). In this paper, several FOSs, which use different optical sensing principles for multiple physical parameter measurements of EMs, are reviewed. This paper also provides an insight into the major developments, and discusses the engineering challenges of FOS used for EM monitoring over the last few decades, and compares the advanced features of FOS with those of conventional sensors in use. Finally, a novel FOS-EM observer system scheme employing the Fibre Bragg Grating technique for multi-parameter monitoring of EM health is proposed, after discussion of the preceding industrial and academic FOS cases for EM applications.

This paper studies bright highly dispersive optical solitons that are with nonlocal type of nonlinearity. The numerical scheme, adopted in the paper, is Laplace-Adomian method. The analytical results, reported earlier, and the numerical results from the current work, agree with an impressively small error measure.

The dispersion of optical fiber can damage optical information, thus limiting data transfer speed and transmission distances. In this paper, a new structure is presented by applying metal nanoparticles for photonic crystal fibers (PCF) so that minimizes dispersion and optical loss. The proposed PCF uses circular and elliptical shape nanoparticles, then their number and location is optimized by PSO algorithm. Applying metal nanoparticles in PCF substrate causes increases the conductivity and increases light excitation, which increases light absorption and decreasing dispersion. By changing the shape, location, and type of nanoparticles, a structure with minimal dispersion and light loss is provided. In this paper, we applied three elliptical and three circular nanoparticles using the PSO results. The hexagonal PCF is designed with air grids and radius of 5.8 µm, and then circular and elliptical gold particles are used instead of air holes. Simulation results show that the loss is 7e−4 dB/cm at wavelengths between 1.3 and 1.65 µm and the dispersion is obtained less than 0.3 ps/nm/km. The light loss and dispersion are reduced compared to other related studies.

A MoS2-Graphene hybrid layer Based High Performance Refractive Index SPR Sensor is illustrated in this paper. Intended for the enhancement of sensor angular sensitivity (S), signal to noise ratio (SNR), quality factor (QF), first of all, the impact of gold layer thickness is investigated and optimized to 40 nm, after then the MoS2 and graphene coting layers are optimized to four (4) and three (3) layers, respectively. Further that, at this optimum structure, the minimum reflectance and SPR angle are decorated. It is seen that the angular sensitivity of the optimum assembly, improved to excellent value of 130 deg-RIU−1 with improved angular SNR of 1.37 and QF of 17.02 RIU−1. At the end of this paper, an analysis specifically for numerically DNA hybridization is considered.

Free space optical (FSO) communication system has obtained significant importance in communication field due to its unique features: unlimited spectrum, larger bandwidth and high data rate, low mass and less power requirements, quick and easy deployability. FSO system better suits in disaster recovery, defense and last mile problems in networks, remote sensing and so on. However, FSO system has greater advantage, its performance is mainly degraded by adverse effects like beam wandering and spreading, scattering and mainly a major degradation factor is atmospheric turbulence and pointing errors which leads to severe degradation in Bit error rate (BER) and Signal to noise ratio (SNR) of the FSO link and makes the communication link infeasible. This paper gives a detailed survey on performance enhancement of FSO communication system and also discusses various channel distribution models and modulation techniques to have high reliability and FSO link availability. In this paper, the various atmospheric effects like turbulence, fog, absorption and scintillation and so on are discussed. The first part of the paper analysis the channel models and the latter part of the paper summarizes the different modulation techniques, diversity techniques and also the comparative study of the (SNR) and (BER) under various atmospheric factors of the FSO system. This survey provides the comprehensive details in order to provide low cost and high capacity FSO link design.

Visible light communication (VLC) is a rising guaranteeing new innovation for optical wireless communication with taking part favorable circumstances not available on radio communication. Especially, as connectivity propagation, both across the world and via the Internet of Things. Any communication system is based on the LED light is luminous to verifying the connection. The major challenge in VLC is how to make a communication system to download data in the dark light when indoor lighting is not needed. This paper explains how visible light can be used to transmit data even when the light appears dark or off. We investigate VLC minimum illumination to receive power, to enable users to receive data when the light is “OFF”. This paper focuses on improving the system performance including signal to noise ratio, required power and bit error rate. VLC with different modulation schemes highlighting as the On–OFF Keying, Pulse Position Modulation, L-Pulse Position Modulation, and Inverse L-Pulse Position Modulation are investigated in the dark light for communication. A short part of Pulse Width Modulation is used for dimming illumination. The paper examines the selected parameters and essential requirements of VLC dark light system which are power, bandwidth efficiency and the dimming factor of light sources. We confirm that dark light is enough to keep up information paces of a few kbps. This looks good for the eventual fate of VLC for actualizing shrewd lighting systems.

The large differences between the refractive index of Si and SiO2 in the SOI composite (silicon on insulator) and, as a result, its high ability to trap lasers, have led to the construction of valuable optical equipment in recent years. In this paper, with a new idea, by adding two reciprocating golden walls and a transverse air gap, the SOI structure is developed in such a way that equipment made with the new method, such as XOR and NOT gates and power-phase comparators, have a dreamy speed and a super small size. This structure is only compatible with linear polarization so that the axis of polarization, which is the direction of the electric field, is parallel to the gold plates. In the multifunctional structure presented in this paper, if the inputs are uniform plane waves, the output will be uniform plane wave with high accuracy and that the inputs can be phase or power while the output is only power. Simulation in this paper is done using finite-difference-time-domain method.

The aim of the paper is to see the influence of Franckeite on the sensing application of SPR based biosensor. Franckeite is an emerging (2D) material from sulfosalt family having naturally presented spontaneously vander Waals (vdW) Heterostructure. We have investigated and carried out detailed analysis to design the high-performance biosensor by exploiting the unique properties of Franckeite. The performance of the biosensor is quantified in terms of Sensitivity and other performance parameters. Proposed work is theoretical where we have proposed a surface plasmon resonance (SPR) biosensor in combination of the nanosheets of (Bimetallic layer + Franckeite + TMDC + BP) in order to enhance the sensitivity. It’s also shown in the paper that by sandwiching a buffer (polymer) with low refractive index (close to water) between metal layer (Au in this case) and dielectric medium prism, the value of FWHM reduced dramatically and significant enhancement observed in FOM (100RIU−1) and detection accuracy (2.38 deg−1). We have also illustrated the concept of long range –SPR (LRSPR) in this paper by giving the comparative analysis of different polymers. As an air-stable 2D material, we expect that 2D Franckeite Nano sheets could have potential applications in the field of chemical as well as biosensing application in the future.

The aim of this work is to point out the current possibilities of using polarized light in sensor technology. Furthermore, the aim is to demonstrate the possibility of using the fiber sensor of thermal field disturbance as a truly feasible biomedical sensor applicable in medicine and especially to analyse different ways of measuring polarization changes. This paper concludes theoretical and experimental study deal with temperature response of birefringent fiber. It is supposed to use it for design of sensor of temperature disturbance. The paper follows up on the previous works, where the response of the birefringent PANDA fiber to thermal exposure in the temperature range from 0 to 48 °C was studied. These experiments analyzed the dynamic sensitivity characteristic of birefringent fiber for the process of thermal source apposition. The present paper brings a detailed comparative analysis of fiber response to the processes of apposition and the removal of thermal source, which are evaluated from the point of view of the system’s response after the ending of the thermal exposure. For practical use in fiber recovery analyses, the phase development rotation senses are described on the observable Poincare sphere.

In this paper, we derive analytical expressions for the spatial evolution of the instantaneous Poynting vector for the transverse magnetic (TM) surface plasmon (SP) modes of a symmetric planar dielectric-metal-dielectric optical waveguide. We discuss the behaviour of the Poynting vector in the metal film due to the optical absorption of electromagnetic waves propagating through the medium to excite the surface plasmons in a resonant manner in the metal film at the interface. This optical absorption of the electromagnetic waves results in a finite propagation length of SP modes. We derive an analytical formula for the penetration depth of the instantaneous Poynting vector in the dielectric cladding regions and show that it is different as compared to the penetration depth of the average Poynting vector. We utilize this analytical formula to calculate the optimum thickness of the affinity layer in a graphene-based surface plasmon resonance (SPR) biosensor and analyze its performance in terms of sensitivity and Figure-of-Merit. We also show that our analytical formula can be used to calculate the optimum thickness of a thin high-index dielectric layer which is added to any conventional SPR based sensor to enhance its sensitivity. The optimum thickness thus calculated correlates closely with the experimental results that have been published previously. The analysis done in this paper can also be utilized in calculating the separation between any two adjacent waveguides/optical films which are coupled together evanescently, such as directional couplers and TE/TM polarisers.

In this paper, we have studied the performance evaluation and enhancement of a wavelength-division-multiplexing (WDM) for the passive optical network (PON) in the hybrid fiber/free-space optical (HFFSO) communication system using the modified on–off keying (OOK) based intensity modulation and direct detection (IM/DD) techniques. This work describes the design and analysis of the 8-channels WDM based on the PON-HFFSO transmission system at 2.5 Gbps under different atmospheric turbulence (AT) conditions. Inter-channel crosstalk (ICC), fluctuation, amplified spontaneous emission noise, AT, and impairments are investigated in the paper. A hybrid fiber/WDM-FSO over the PON structure using IM/DD and OOK significantly improves reliability link and accessibility as well as data rate, also improves the system capacity; hence the proposed model will reduce power consumption while maintaining system efficiency. Both impairments and ICC are investigated here and the results are presented in the form of bit-error-rate (BER), transmission distances, the required optical power, and electrical signal-to-noise ratios (SNRs). The system uses the modified OOK based on IM/DD to implement adaptive and electrical SNRs detection thresholds. Numerical results show that the SNR gap between the electrical-SNR-optimized detection system and adaptive detection system is 2.2 dB and 4.2 dB at a BER of 10−5 without a state offset ξ = 0 and ξ = 0.21, respectively. The proposed model enhances performance in terms of BER and electrical SNRs. An improvement in the power penalty of 2.0–4.0 dB at a BER of 10−12 can be potentially achieved using the modified OOK technique when impaired by the weak turbulence.

In this paper, a novel topology for refractive index optical fiber sensors based on surface plasmon resonance (SPR) phenomenon is presented. The fiber core has a graded refractive index and there is a hole at the center of the core which is coated by silver. The analyte is injected into the hole. In our structure, there is no need for removing the cladding of the fiber. Two types of graded refractive index profiles are investigated in this paper. The proposed sensor is simulated using finite difference time domain method. The results show that the presented SPR sensor has a good spectral response and suitable sensory specifications. The sensitivity of the proposed sensor is about 4350 nm/RIU. The figure of merit of this sensor is 149 RIU−1. The proposed sensor can be used for measuring refractive indices between 1.38 and 1.49. As a result, it can be used for bio-sensing applications. One of the advantages of the proposed sensor is that it is label-free.

In this paper, the perturbed nonlinear Schrodinger equation with dual-power law of nonlinearity is studied by adopting four mathematical methods namely the Modified Kudryashov method, the extended Tanh–Coth method, the modified simple equation method and soliton ansatz method. As a results, a set of various types of solitons that contains dark, singular, dark–singular, bright optical solitons and other form of optical soliton solutions are obtained. Firstly, we solve the perturbed nonlinear Schrodinger equation by considering the dual power law parameter using the first three integration methods and secondly we set this parameter equal to one in order, to solve the problem with the fourth method. The used methods in this paper present various applications in fields of nonlinear wave equations. Comparing our new results with well-known in literature are also given. Moreover, the graphical representations of the modulus of some optical soliton solutions and their 2-D profile are also depicted.

In this paper, a hybrid technique using a precoder and a µ law compander is proposed to alleviate light emitting diode (LED) nonlinearity as well as peak-to-average power ratio (PAPR) reduction in a VLC system. A µ law compander is used to compress the peak valued signal and enhances small amplitudes to lower the PAPR. The work attains optimal PAPR and improves bit error rate (BER) of the system at low signal to noise ratio values. The nonlinear characteristic of a LED used as the transmitter in a VLC system leads to damaging effects while using OFDM in an optical system. The combination scheme improves LED nonlinearity for low input back off (IBO) power. In the work, nonlinearity is characterized using error vector magnitude (EVM) in percentage. The proposed method shows a 5% EVM improvement for 0 dB IBO. The paper provides a choice for a trade-off among PAPR reduction, BER and reduced nonlinearity.

In this paper, we propose a new design of plasmonic organic solar cells (OSCs). It consists of a protective layer of SiO2, an anti-reflective glass of ITO, a compact buffer of PEDOT:PSS, an absorbing organic material of P3HT:PCBM, and a reflective layer of Al. A square periodic array of core–shell nanoparticles (Au@ITO NPs) is embedded in the active layer of P3HT:PCBM in order to enhance the absorption of OSC. Although ITO coating slightly reduces efficiency, it prevents the oxidation of gold NPs and increases the OSC lifetime. We study the effect of numerous parameters such as the core radius, shell thickness, and core material on the optical absorption by solving Maxwell’s equations using the three-dimensional finite-difference time-domain method. The drift–diffusion and Poisson’s equations are solved with an in-house software tool by discretizing the solar cell using the finite element method. To the best of our knowledge, this paper is the first to apply the real model of trap-assisted recombination and Auger recombination of used materials to the simulations to match them with the experimental results. The numerical results show the proposed OSC embedded with Au@ITO NPs has the built-in potential of 2.9 V, short-circuit current of 16.63 mA/cm2, the open-circuit voltage of 1.14 V, maximum power of 17.25 mW/cm2, fill-factor of 0.91, the conduction band of 2.8 eV, electron quasi-Fermi level of 2.35 eV, hole quasi-Fermi level of 0.6 eV and an efficiency of 17.25%. Furthermore, the performance of the proposed OSC has an improvement of 25% compared to conventional OSCs.

The fiber optic link is one of the main segments of up-to-date telecommunication systems. Developing low cost, ultra reliable systems with very low latency for massive machine to machine and enhanced broadband mobile networks is a hot research topic. Motivated by this we investigated the polarization multiplexing technique applicable in fiber optic links because it can be used for increasing the transmission capacity. In the present paper a novel approach, the double polarization multiplex method is investigated. In that case the crosstalk between two polarization states is one of the main issues. As a result of crosstalk, the two channels composed by double polarization can disturb each other significantly. Crosstalk can appear due to any imperfection in the fiber and in the optical circuitry of the transmitter and receiver. In this paper, we propose a new method for reducing the effect of crosstalk even in the case of high-speed long-distance transmission. The applicability of the new concept is validated by experiments. A bit error rate better than 10−6 has been achieved over a 7 km long fiber carrying 12 Gbit/s NRZ modulation. That result is significantly better than the already published experimental data using 2, 5 Gbit/s bit rate. The cross polarization discrimination is also improved by 10–15 dB.

The optical response to the linear and circular polarized light of the double-spirals structures are investigated by the finite element simulation in this paper. For the linear polarized light the double-spirals structures are like a linear polarizer in the long wavelength region with the wavelength of 900–1500 nm, which corresponds to the standing-wave mode of a single spiral. The double-spirals structures have evident chiral effect in the long wavelength, and has 3–4 circular dichroism (CD) peaks in the wavelength range 850–1500 nm. For all structures investigated in this paper, the CD spectra have obvious blue shift with the increase of the arm width. The simulation results also indicate that the smaller the distance between the two spirals, the more the chiral effect of the double-spirals structures. The chiral effect for both structures with the distance of 400 nm diminishes, and both structures no longer have typical CD spectra.

In this paper, an optical absorber based is exploited on self-similar cylindrical for material detection in the infrared spectrum as a refractive index sensor. Two models are suggested and the effect of the gaps is discussed. Actually, the gaps can be used for intensifying the absorption and improving the figure of merit (FOM). The absorber is modified for 300 THz (1000 nm) with reflection value of − 45 dB (0.004) which is made this absorber as a good choice for optical refractive sensing. This study shows the importance of the parasitic elements and gaps for improving the sensing quality and FOM value. In fact, the reflection of the Nanoabsorber is increased extremely without using the parasitic element up to − 14 dB. As shown in this paper, the FOM of the prototype absorber is enhanced more than 10 times for some refractive indexes by implementing of gaps. The maximum value of the FOM is 400 RIU−1 for the final model with gap and the maximum sensitivity is 204 nm/RIU obtained for the structure without the gap. In brief, these gaps can be considered for increasing the FOM more than the basic model.

High sensitivity and rapid detecting photonic sensors are essential devices such as in medical diagnostics and biological test. Conventional biochemical sensors based on the directional couplers need other apparatus to measure the precise output power intensities. Conversely, a digital sensor is more efficiently utilized to determine the refractive index of the liquid sample. By simple mathematics induction, the formulae of designing a general photonic digital sensor, which comprises k (k ≥ 1) levels of the directional couplers composed of the ridge waveguides, are obtained in this paper. The performance of the sensor resembles an analog-to-digital converter and distinguishes 2k liquid samples. As long as k is large enough, the sensor can lower the quantization error and precisely determine the refractive index of the liquid sample. To demonstrate the validity of our formulae and design rules, we present the beam propagation method simulation results in this paper.