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Efficient mid-infrared (MIR) optical modulator is reported and numerically analyzed for both the transverse electric (TE) and transverse magnetic (TM) polarized modes. The proposed design is based on the silicon-on-calcium-fluoride platform with vanadium dioxide (VO2) as a phase changing material. Due to the attractive property of its phase transition between dielectric (ON) and metallic (OFF) states under the effect of an applied electric field, VO2 is utilized to enable the modulation process. At an operating wavelength of 3.5 μm, the reported modulator realizes an extinction ratio (ER) of 10.9 dB/μm with an insertion loss (IL) of 0.24 dB/μm for the TE polarized mode. However, for the TM polarized mode, an ER, and IL of 9.5 dB/μm, and 0.19 dB/μm, respectively are achieved. Additionally, the suggested design has a good fabrication tolerance of ± 10% where the ER is better than 10.4 dB/μm and 8.6 dB/μm for the TE and TM polarized modes with IL less than 0.26 dB/ μm. Therefore, the suggested modulator can play a pivotal role in different MIR applications including imaging, sensing, security, and communications.

In this paper, a novel design of superlens based on photonic bandgap structure for high resolution point spread function (PSF) is reported at a wavelength of 3 μm. The lens is able to generate a non-diffraction Bessel beam with a number of focusing points with variant resolution limits. The optimized structure provides high resolution in both lateral and axial directions. The maximum achieved lateral resolution of PSF is down to ~ 0.27λ with corresponding axial resolution down to ~ 0.57λ attaining a FOM, the inverse of the product of both resolution limits, of ~ 6.49. Meanwhile, the maximum axial resolution is down to ~ 0.4λ with corresponding lateral resolution down to ~ 0.33λ with a FOM of ~ 7.34. In addition, the proposed design is able to generate a focusing point extended in space up to ~ 0.98 µm with a sub-diffraction lateral resolution down to ~ 0.47λ. Furthermore, the reported superlens demonstrates a sub-diffraction focusing in lateral direction along the range the bandgap wavelengths (from 2.4 to 3.6 µm) showing a significant increase of focal depth when decreasing the operating wavelength. Remarkably, a high focal depth up to ~ 1.77 µm is achieved at the operating wavelength of 2.6 µm. The suggested design has a tremendous potential in 3D biological imaging and biosensing applications.

Thin-film organic photovoltaic (OPV) devices represent an attractive alternative to conventional silicon solar cells due to their lightweight, flexibility, and low cost. However, the relatively low optical absorption of the OPV active layers still represents an open issue in view of efficient devices that cannot be addressed by adopting conventional light coupling strategies derived from thick PV absorbers. The light coupling to thin-film solar cells can be boosted by nanostructuring the device interfaces at the subwavelength scale. Here, we demonstrate broadband and omnidirectional photon harvesting in thin-film OPV devices enabled by highly ordered one-dimensional (1D) arrays of nanogrooves. Laser interference lithography, in combination with reactive ion etching (RIE), provides the controlled tailoring of the height and periodicity of the silica grooves, enabling effective tuning of the anti-reflection properties in the active organic layer (PTB7:PCBM). With this strategy, we demonstrate a strong enhancement of the optical absorption, as high as 19% with respect to a flat device, over a broadband visible and near-infrared spectrum. The OPV device supported on these optimized nanogrooved substrates yields a 14% increase in short-circuit current over the corresponding flat device, highlighting the potential of this large-scale light-harvesting strategy in the broader context of thin-film technologies.

A novel design of surface plasmon (SP) photonic crystal fiber (PCF) for DNA hybridization detection is proposed and analyzed. The suggested biosensor relies on plasmonic D-shaped PCF configuration. Accordingly, the core guided mode in the silica core is coupled with the SP mode near the plasmonic layer. The resonance wavelength is sensitive to the DNA hybridization process. Therefore, the suggested bio-sensor is studied to maximize the DNA hybridization detection sensitivity by adjusting the structural geometrical parameters. The numerical results are obtained using full vectorial finite element method with perfectly matched layer boundary condition and non-uniform meshing capabilities. The reported D-shaped PCF offers high wavelength sensitivity of 405.4 nm/RIU with a corresponding amplitude sensitivity of 5.65 RIU−1. Consequently, the applications based on DNA classification can be potentially implemented by the reported biosensor.

A novel design of metamaterial biosensor for cancer early detection is proposed and analyzed. The suggested structure is based on two loops of hexagonal gold layers on a polyamide substrate. High field confinement is obtained in the sensing region with high absorption of 0.999 and high quality factor of 11.33 at f = 3.15 THz. The resonance frequency is sensitive to the sample refractive index variation. Therefore, high average sensitivity of 1649.8 GHz/RIU is achieved for cancer early detection through basal cell, breast cell, bervical cell, jurkat, MCF-7, and PC12. Further, high linear performance is obtained with good robustness against fabrication imperfection. The analysis is carried out using full vectorial finite element method.

In this letter, a scalar non-iterative bi-directional finite element based beam propagation method (NI-BiBPM) is proposed for the analysis of light propagation in photonic devices with circular symmetry. We adopt the Blocked Schur algorithm (BSA) for calculating the square root of the characteristic matrix in order to achieve fast and stable results and to avoid the complications and limitations of other computational modeling techniques such as Taylor or Pade approximations. The suggested NI-BiBPM approach does not only offer reduction in execution time and memory requirements but also guarantees the numerical stability.

A Finite Difference Time Domain (FDTD) analysis has been effectively applied to investigate the transmission of the transverse electric polarized pulses in photonic crystals arrangements. The photonic bandgap of 2-D photonic crystal with square and veins lattices has been calculated using three methods Band structure, transmission diagram and defected structures, and comparison with published results are done and excellent agreement are obtained, Moreover, two different photonic crystal devices are analyzed Index Terms: Photonic Crystal [PC], Finite Difference Time Domain (FDTD), Photonic Bandgap (PBG).

Ultra-compact transverse magnetic (TM)-pass polarizer based on silicon on sapphire (SOS) platform is proposed and analysed. Low power consumption, high linearity and high speed of transmission are the major advantages of the SOS platform in different commercial applications especially in the mid infrared region.The suggested structure has bimetallic configuration of aluminium doped zinc oxide (AZO) and zirconium nitride (ZrN) to highly attenuate the quasi transverse electric (TE) mode. This is due to the coupling between the fundamental TE and the surface plasmon modes. However, the transverse magnetic mode can propagate with minimal losses. At 2.0 µm operating wavelength, the proposed TM-pass polarizer realizes 20.3 dB extinction ratio (ER) with 0.14 dB insertion loss (IL) at a device length of 3.0 µm. Therefore, the reported design has advantages of compact length, high efficiency and CMOS-compatibility.

In this article, the gradient smoothing method is introduced for the first time to the time domain analysis of photonic devices. The proposed method combines the advantages of finite difference and finite element methods. It is capable of accurately modelling irregularly-shaped geometries by dividing the computational domain into elements like the finite element method. While it naturally produces a diagonal matrix for the field discretization similar to the finite difference method which makes it a perfect method for explicit time marching schemes. The beam propagation method with explicit time discretization is adopted for the propagation in time. Additionally, a novel stretched coordinate perfectly matched layer with two auxiliary equations is developed for the proposed method. The numerical aspects of the proposed method are demonstrated through the analysis of different photonic integrated structures.

A novel design of thin-film crystalline silicon solar cell (TF C-Si-SC) is proposed and numerically analyzed. The reported SC has 1.0 µm thickness of C-Si with embedded dielectric silicon dioxide nanowires (NWs). The introduced NWs increase the light scattering in the active layer which improves the optical path length and hence the light absorption. The SC geometry has been optimized using particle swarm optimization (PSO) technique to improve the optical and electrical characteristics. The suggested TF C-Si-SC with two embedded NWs offers photocurrent density ($${J}_{ph}$$ J ph ) of 32.8 mA cm−2 which is higher than 18 mA cm−2 of the conventional thin film SC with an enhancement of 82.2%. Further, a power conversion efficiency of 15.9% is achieved using the reported SC.

The optimum choice of the ligand that stabilizes the colloidal quantum dots and passivate the surface is crucial for tuning the energy level and remain elusive. The atomic ligand passivation with iodide remains superior over other surface treatments. Herein, we applied the iodide ligand to passivate the CdSe nanocrystals with an excitonic absorption at 2.1 eV by a liquid-liquid extraction process. We took the view of the change in the optical and structural properties upon ligand exchange. Finally, we tested the performance of the iodide treated dots by employing it in an inverted structure polymer solar cell based on P3HT: PCBM.

Synthesizing nanoparticles (NPs) capable of hindrance the microbial colonization is a global demand. Such NPs can prevent emerging infectious diseases that harm the public health. In this paper, a co-precipitation method is employed to synthesize colloidal of metal iodide, namely copper iodide (CuI), silver iodide (AgI), and lead iodide (PbI2). Subsequently, EDS, XRD, HRSEM with mapping technique are conducted to study the structural properties of the as-synthesized samples. Additionally, their absorption is highlighted using UV/Vis spectroscopy. NPs with average crystallite size equals to 54.98, 57.02, and 23.47 nm for PbI2, CuI, and AgI, respectively are calculated. SEM images show that PbI2 consists of randomly-oriented dense nanoflakes of iodide. CuI NPs have a dense medium with tiny particles adhered to larger particles related to copper. Further, AgI sample contains agglomerated crystallites with a combination of small and large sizes. Antimicrobial activity of the samples against all tested standard pathogens is examined. In particular, AgI NPs have a prominent antimicrobial capability against Escherichia coli, Candida albicans and Staphylococcus aureus (ZOI of 18.0, 16.0 and 15.0 mm, respectively). Therefore, the AgI NPs can be safely used in solving serious industrial, pharmaceutical and medical challenges and particularly in the treatment of surface infectious diseases.

Inorganic–organic hybrid perovskite solar cells (PSCs) have recently seen considerable progress, and this has encouraged researchers to evolve and test numerous different and potentially improved device architectures. As a result, in this paper, a theoretical design for improving light absorption to obtain maximum photocurrent using NiO/GeSe core–shell nanostructures is introduced. The effects of using nanostructure arrays, based on the light trapping technique, on the light absorption, generation of carriers, absorption field profiles, and finally the photocurrent density of PSCs, have been investigated through a three-dimensional finite-difference time-domain approach. By selecting NiO and GeSe as the core and the shell materials, the absorption of the active layer has been increased, relative to the use of a conventional planar structure. This core–shell nanostructure leads to a reduction in the carrier recombination within the PSC proposed design. The results obtained from our simulation show that the device performance is highly dependent on the height and materials used in the core–shell. Significantly, an optimal height of 160 nm was obtained for core–shell in a PSC design with a J ph value of 27.23 m A / c m 2 .

In this paper, an optical modulator design based on a silicon-on-calcium fluoride platform with a layer of Vanadium dioxide (VO2) is proposed. The VO2 as a phase changing material is used to control the modulation process, making use of the phase transition of the VO2 material between dielectric and metallic states. The modal properties of the proposed optical modulator are studied and analyzed using the well-known full vectorial finite element method. Whereas, the light propagation is studied using the 3D finite difference time domain method. The suggested device offers a number of advantages such as low insertion loss of 0.431 dB/µm and high extinction ratio of 14.99 dB/µm at a wavelength of 3.95 µm and device length LD of 2 µm. To the best of the authors’ knowledge, this is the first time to present an infrared optical modulator based on silicon-on-calcium fluoride platform.

A highly sensitive 2D Si photonic crystal (PhC) sensor is proposed and analyzed for the detection of gamma-ray doses in the visible light region. The suggested PhC has a cavity infiltrated by poly-vinyl alcohol (PVA) polymer doped with crystal violet and carbol fuchsine dyes. The transmission through the proposed design has a peak at the resonance frequency, which is sensitive to the gamma-ray doses. The geometrical parameters of the suggested PhC are studied to maximize the sensor sensitivity, quality factor, and normalized transmission. The proposed sensor achieves high sensitivity of 150 nm per refractive index unit (nm/RIU) with high linearity and high-quality factor (Q) of 808. The analysis is carried out using full-vectorial finite-element method and the plane wave expansion method. To the best of the author's knowledge, it is the first time to use 2D-PhC technology for gamma-ray detection.

The generation of high-fidelity polarization-entangled photon pairs, to date, has been demonstrated on specific spatial modes or over relatively narrow apertures. We put forward and demonstrate an experimental scheme to extend the temporal and spatial indistinguishability of polarization-entangled photons over wide emission angles, which can be applied to cover the whole SPDC cone. Over such wide angular extent, while the time-delay map is almost flat which renders the conventional compensation via a birefringent element an appropriate approach, the relative-phase map -- verified as a quadratic function -- necessitates a tunable compensation paradigm. Here, to do so, we employ a phase-only two-dimensional spatial light modulator (2D SLM) loaded by the complementary of the relative phase map to equalize the phase variations for one third of the noncollinear spontaneous parametric down conversion (SPDC) emission. After eliminating the temporal and spatial distinguishability over the 2D SLM area, a 97% polarization visibility is verified for the entangled photon pairs scattered widely across the SPDC cone., 6 pages, 4 figures

This paper presents two efficient tunable plasmonic mode converters in the infrared regime. The proposed configurations consist of silver layer with etched rectangular holes as metal insulator metal (MIM) waveguides with central cavities. The holes are infiltrated by nematic liquid crystal (NLC) material to increase the transmission through the suggested designs. Additionally, the NLC is used to have tunable operation where the modes at the output port can be controlled. The simulations are carried out using full vectorial finite element (FEM) method. The first design has a single output port which converts the TM mode into the TEM mode with high transmission conversion efficiency of 70%. Further, the second structure allows the generation of the two plasmonic modes simultaneously in two output waveguides. During the biased state, the s- mode transmission conversion efficiency reaches 50% while the transmission of a- mode at the unbiased state is equal to 49%. It is expected that the proposed tunable mode converters will play an important role in the development of the plasmonic-photonic circuits.

Laser shock peening (LSP) is a surface treatment process for increasing the strength and reliability of metal components. Traditionally applied to composite structures of automotive and medical applications, the LSP technology also shows great potential for aircraft parts to improve the fatigue resistance of highly stressed critical aircraft turbine engine components, complex forming of wing surfaces, steam turbines, etc. The present study investigates the effect of laser peening without coating on the hardness of an aluminium alloy. The Vickers micro-hardness test is used to study the hardness of the Al alloy with different wavelengths and laser intensities. It is found that the metal hardness can be significantly increased to more than 80% by increasing the laser intensity and the number of laser shots irradiated per unit area.

A novel design of nearly perfect metamaterial absorber is proposed and analyzed for terahertz sensing applications. The full vectorial finite element method is used to simulate and analyze the reported design. The suggested structure is based on increasing the confinement of both electric and magnetic fields simultaneously at the resonance frequency. Therefore, an absorptivity of 0.99 is achieved at 2.249 THz with a narrow resonant peak and a $Q$ -factor of 22.05. The resonance frequency is sensitive to the surrounding medium refractive index at fixed analyte thickness. Consequently, the reported metamaterial design can be used as a refractive index (RI) sensor with the high sensitivity of 300 GHz/RIU and the figure of merit (FoM) of 2.94 through an RI range from 1.0 to 1.39 at the analyte thickness of $1.0~ \mu \text{m}$ . Furthermore, the proposed sensor has a sensitivity of 23.7 GHz/ $\mu \text{m}$ for the detection of the sensing layer thickness variation at the fixed analyte RI of 1.35. It is worth noting that most of the biomedical samples have a refractive index range from 1.3 to 1.39. Therefore, the reported sensor can be used for biomedical applications with high sensitivity.

In this paper, we present a polarization-assisted $L$ -ary differential phase-shift keying multipulse pulse-position modulation (PA. $L$ DPSK-MPPM) technique that is secured in the physical layer by a discrete-chaos system. The all-optical PA. $L$ DPSK-MPPM scheme benefits from the polarization as an additional degree of freedom which greatly reduces the system complexity relative to prior implementations. The discrete-chaos scrambling is based on a message-seeded two-dimensional chaotic map tailored for independent perturbation of the occupied time-slot positions (MPPM information) and their relative phase shift ( $L$ DPSK information). Synchronized and non-synchronized implementations of the chaotic PA. $L$ DPSK-MPPM technique are proposed with expressions for the corresponding spectral efficiencies being determined and compared with prior $L$ DPSK-MPPM setups. The performance of PA. $L$ DPSK-MPPM under gamma-gamma (GG) free-space optical (FSO) fading channels is analytically verified to outperform the prior designs for different FSO channel states which is supplemented by Monte Carlo (MC) simulations. The system security is numerically examined against various types of attacks, including brute-force, differential, and statistical attacks.

A novel design of circular photonic crystal fiber (C-PCF) gas sensor is presented and analyzed by full vectorial finite element method. The suggested structure has a spiral porous Core region to achieve high light interaction with the applied gas. The geometrical parameters of the proposed sensor are studied to achieve high sensor sensitivity. The introduced C-PCF offers high relative sensitivity of 72.04% at a wavelength of 1.33 μm. The reported gas sensor also offers a compact, accurate and useful tool for detecting harmful gases over a wide transmission band from wavelength of 1 μm to 1.8 μm.