Showing papers in "Journal of Optics in 2021"

Highly dispersive optical solitons in birefringent fibers with four nonlinear forms using Kudryashov's approach

Abstract: This paper exhibits bright, dark, singular as well as combo optical highly dispersive solitons in birefringent fibers. The governing model is considered with four forms of nonlinear refractive index. The existence criteria for such solitons are also listed.

Optical polarization skyrmionic fields in free space

Abstract: We construct optical beams in free space with robust skyrmionic structures in their polarization fields, both in the electric spin vector for near-circular fields and in the polarization direction for near-linear fields, and for both Bloch (spiral) and Neel (hedgehog) textures. These structures are made possible by the spin-orbit coupling of tightly-focused nonparaxial optics as applied to higher-order Full-Poincare beams, as well as by standing-wave configurations comprising forwards- and backwards-propagating waves. Our constructions show near-uniform circular and linear polarizations, providing a high degree of topological protection in the absence of nonlinear interactions, and they open the door to the use of topological light for the creation, detection and manipulation of skyrmions in magnetic devices and spinor condensates.

Studies on crystal structure, morphology, optical and photoluminescence properties of flake-like Sb doped Y2O3 nanostructures

Abstract: In the present research work, Sb doped Y2O3 nano structures (NS) with different concentrations (5%, 8% and 10%) synthesized by self propogating room temperature method. Nanostructures are characterized by UV–visible, XRD (X-ray diffraction), SEM (scanning electron microscopy) and XPS (X-ray photoelectron) spectroscopic techniques. Flake-like morphology of the NS observed in SEM analysis having grain size varies in between 65 and 93 nm. Chemical composition of the constituent elements has been determined from XPS analysis with Sb 3d3/2, Sb 3d5/2, Y 3d3/2 and Y 3d5/2 binding energies appeared at 540 eV, 530 eV, 165.8 eV and 154.4 eV, respectively. XRD pattern depicted mixed phase of cubic crystal structure with crystallite size lying between 36.8 and 29.9 nm. Red shift in the optical absorptivity was observed in the spectrum, and spectral shift from ultraviolet to visible region with optical band gap (Eg) value decreases from 3.36 to 1.98 eV. Upon excitation with ultraviolet radiation (λexcitation = 280 nm), NS showed red emission in all concentrations of Sb dopant and maximal emission intensity appeared at 475.5 nm for 10% of Sb dopant concentration. The NS finds prominent utility in the field of optoelectronics and photoelectronics applications.

Cubic–quartic optical soliton perturbation with Lakshmanan–Porsezian–Daniel model by sine-Gordon equation approach

Abstract: This paper recovers cubic–quartic optical solitons for perturbed Lakshmanan–Porsezian–Daniel model. This is for both with and without polarization. The sine-Gordon equation approach is the scheme adopted to retrieve the soliton solutions. A full spectrum of soliton solutions have emerged.

Photoconductive emitters for pulsed terahertz generation

Abstract: Conceived over 30 years ago, photoconductive (PC) emitters have proved essential in the development and spread of terahertz technology. Since then, not only have they been used extensively in a wide range of spectroscopic and imaging applications, they have also undergone significant improvements in performance, leading to their use for broadband or non-linear spectroscopy. In this review article, we provide an overview of the literature, highlighting the key milestones in the progression of the PC emitter. We also investigate the future of PC technology and review the existing challenges.

Optical soliton structure of the sub-10-fs-pulse propagation model

Abstract: This research paper illustrates a novel structure of the optical soliton wave solutions of nonlinear Schrodinger (NLS) equation with the higher-order (a model for the sub-10-fs-pulse propagation) by using the modified Khater method. Moreover, this research is studying the stability properties of obtained solutions to show their ability to apply in the model’s applications. The NLS equation with the higher-order describes the quantum aspects of a quantum-mechanical system. Some sketches are plotted to show more physical properties of the real, imaginary, and absolute obtained solutions. All obtained solutions are verified of its accuracy by putting them back into the original equation.

Saturable higher nonlinearity effects on the modulational instabilities in three-core triangular configuration couplers

Abstract: This paper demonstrates the possibility to observe the modulational instability (MI) regions due to modified nonlinear saturability over and above other high-order nonlinearities for the triangular configuration of a three-core oppositely directed coupler. In this configuration, two channels are positive-refractive-index material, and one is a negative-index material. The governing equations are the modified coupled nonlinear Schrödinger equations, to which we add the higher-order nonlinearity terms and coupling terms. This equation is further modified with the saturable nonlinearity term. In the presence of several nonlinearities, we derive the dispersion relation for the optical coupler under consideration. We use a linear stability analysis to study the modulation stability characteristic gain in both the normal and anomalous group-velocity dispersion regimes. We have widely varied the parameter range of the physical system parameters to accommodate different possibilities. In the normal region, the saturable nonlinearity aids in increasing the bandwidth of the MI region, while in the anomalous regime, the bandwidth reduces. In the normal dispersion case, the simultaneous presence of all nonlinearities in the optical coupler does not provide a suitable scope for pulse propagation. On the other hand, in the anomalous regime, these nonlinearities favor for pulse propagation.

Highly dispersive optical solitons with quadratic–cubic law of refractive index by the variational iteration method

Abstract: This paper studies highly dispersive bright and dark optical solitons from a numerical perspective by variational iteration method. This is a very efficient algorithm that has gained popularity to numerically address model equations from a range of physical phenomena including photonics sciences. The current paper studies highly dispersive optical soliton solutions that are considered with quadratic–cubic nonlinear form of refractive index, modeled by the nonlinear Schrodinger’s equation. The novelty of this approach is that it recovers bright and dark soliton solutions to the model numerically, and the error of approximation has also been presented. The algorithm displays the solutions with an impressive error measure.

Enhanced mid-infrared gas absorption spectroscopic detection using chalcogenide or porous germanium waveguides

Abstract: Different integrated photonic sensors are investigated for the detection in the mid-infrared region of the two gases namely CO2 and CH4. The three studied structures are ridge waveguides, based both on chalcogenide films (ChG) or porous germanium (PGe) and slot waveguides based on ChG. Waveguide dimensions are optimized to obtain the highest power factor between guided light and gas while maintaining a single mode propagation in the mid-infrared wavelength range. The achievable power factor is 1% in case of ChG ridge-waveguide, 45% for PGe-ridge, and 58% in case of ChG-slot. Extremely low limits of detection (LOD), 0.1 ppm for CO2 at λ = 4.3 μm and 1.66 ppm for CH4 at λ = 7.7 μm are obtained for a ChG slot waveguide, due to the large gas absorption coefficients in the mid-infrared spectral range. For PGe waveguides, low LOD values are also computed: 0.12 ppm for CO2 at λ = 4.3 μm and 1.89 ppm for CH4 at λ = 7.7 μm. These results show that the proposed structures could achieve competitive performance required for generic spectroscopic detection on a chip for environment and health sensing.

Design of a large bandwidth 2 2 interferometric switching cell based on a sub-wavelength grating

Abstract: In the last few decades, increasing research effort has focused on the design of telecommunication payload systems with advanced features and lower costs in space applications. In this context, photonic solutions have already proven the potential to achieve additional functionalities, such as multiplexing or switching of RF or microwave signals, with consequent additional benefits in terms of size and mass reduction. In this paper, we report on the design of a 2 × 2 switching cell based on a thermo-optic interferometric configuration, whose key element is a sub-wavelength grating. We have theoretically demonstrated a broadband operation, with better performance in terms of operating wavelength range and compactness with respect to the existing interferometric cells. The switching cell shows a worst extinction ratio of about 13 dB, insertion loss of less than 2 dB, crosstalk of 12 dB, over a bandwidth of 150 nm, within a footprint as small as 240 µm × 9 µm. To demonstrate its potential use as a routing fabric in flexible telecommunication satellite payloads, as an example, the designed switching cell has been used as a building block of an 8 × 8 dilated Banyan matrix, where large bandwidth (150 nm), low crosstalk (−38 dB), small footprint (≈1620 µm × 576 µm) and relatively low power consumption (276 mW) have been achieved.

Cubic–quartic optical soliton perturbation and conservation laws with generalized Kudryashov’s form of refractive index

Abstract: This paper obtains cubic–quartic optical solitons of generalized Kudryashov’s law of refractive index. The included perturbation terms are with maximum intensity. The retrieved soliton solutions are with the aid of F-expansion, exp-expansion and Riccati equation methods. Finally, the conservation laws of the model are also recovered and listed.

Measures of helicity and chirality of optical vortex beams

Abstract: Analytical forms of the optical helicity and optical chirality of monochromatic Laguerre-Gaussian optical vortex beams are derived up to second order in the paraxial parameter kw0. We show that input linearly polarised optical vortices which possess no optical chirality, helicity or spin densities can acquire them at the focal plane for values of a beam waist w0≈λ via an orbital (OAM) to spin (SAM) angular momentum conversion which is manifest through longitudinal (with respect to the direction of propagation) fields. We place the results into context with respect to the intrinsic and extrinsic nature of SAM and OAM, respectively; the continuity equation which relates the densities of helicity and spin; and the newly coined term 'Kelvin's chirality' which describes the extrinsic, geometrical chirality of structured laser beams. Finally, we compare our work (which agrees with previous studies) to the recent article Koksal, et al. Optics Communications 490, 126907 (2021) which shows conflicting results, highlighting the importance of including all relevant terms to a given order in the paraxial parameter.

FTIR and NIR spectroscopic analyses of Co3O4-doped sodium zinc borate glass matrix

Abstract: In this paper, the samples of network of borate glass have been prepared by melt quenching technique and characterized. Optical characterization of the network was examined By UV–VIS spectroscopic technique. The results showed an increasing in refractive index, permittivity, extinction coefficient, dielectric constants, electric susceptibility and polarizability with increasing Co3O4 content. Cobalt ions produced intense blue color in glass and used as optical filters in UV–VIS region. Fourier-transform infrared spectroscopy is used to characterize the local order and kind of forming structural units and provides information about the interaction between alkali metal ions and borate glass network. Addition modified oxide of cobalt oxide converts some of BO3 to BO4 units. Glass samples are exposed to melting and grinded so the resulted bands are very broadening and overlapping to analyze this overlap used deconvolution analysis technique. Cobalt-doped borate glass behaved as optical band pass filters, i.e., area, center, width and height of band pass.

Numerical investigation of metasurface narrowband perfect absorber and a plasmonic sensor for a near-infrared wavelength range

Abstract: Herein, we have presented a computation study of a metasurface (MS) narrowband perfect absorber performed utilizing the three-dimensional finite element method. In the first part of the paper, the periodic sequence of silicon meta-atoms (MAs) is positioned on a ∼100 nm gold thin-film. The gold thin-film obstructs a broadband light at normal incidence, and silicon MAs are utilized to stimulate the surface plasmon by scattering light through it. The highest absorption of 96% is procured at 930.26 nm in the air medium which can be further enhanced by using a layered structure of MAs deposited on gold. The MAs are composed of Si/SiO2/Si with an optimized layers height. Consequently, the perfect impedance matching of the electric and magnetic dipoles takes place providing a 99% of absorption insensitive to the incidence angle of light and almost negligible reflection at a resonating wavelength of 889.4 nm. This feature allows us to utilize this device as a plasmonic sensor. That is why, in the second part of the paper, the proposed device design is studied for the detection of the refractive index of the surrounding medium. The sensitivity and figure of merits of the MS device are in the range of 460–492 nm RIU−1 and 76.7–82 RIU−1, respectively. We claim that the anticipated MS element can be employed in solar photovoltaic and biomedical sensing purposes.

Vision of IoUT: advances and future trends in optical wireless communication

Abstract: Oceans cover about 72 percent of the Earth’s atmosphere. Owing to distinct incredible aquatic activities the Oceans remain unclear and deep-seated to investigate. “Underwater wireless communication” (UWC) plays an important role in sea species tracking, water contamination, oil and gas production, natural hazard control, maritime security, naval military activities, and in detecting improvements in the aquatic environment. To achieve these applications in an efficient way, a new era name Internet of Underwater Things (IoUT) is introduced. IoUT is a scientific development that could bring a new phase for research, business, and underwater military applications. It also severs as an important feature of 5G and 6G networking systems. The up-coming fifth (5G)- and sixth (6G)-generation connectivity networks are supposed to make tremendous improvement relative to the current fourth-generation systems with some essential and general problems about 5G coverage performance, 6G and high-ability networking networks, huge coverage, low latency, high protection, low power usage, strong knowledge, and stable networking. To encounter the obstacles in 5G networks, innovations like optical (OWC) communication by means of wireless means is utilized. Innovations such as optical wireless communication (OWC) are used to tackle the obstacles in 5G networks. OWC is a better employee for operation in 5G network specifications than other wireless technologies. This paper explains how the OWC strategy would be the best and most effective approach to effectively implement 5G, 6G, and IoUT networks.

Recent developments in polymer optical fiber strain sensors: A short review

Abstract: Polymer optical fiber (POF) strain sensors have attracted increasing attention owing to the unique features of polymer over silica such as lower Young's modulus, larger elastic strain limit, higher fracture toughness, biocompatibility, and lower production cost. Several POF strain sensors have been developed in recent years for applications in various technological fields, including structural health monitoring in civil construction and aerospace industries, biomedicine, and robotics. The principles of operation, prospects, and challenges of the POF strain sensors are discussed in this article under five broad categories: POF fiber Bragg grating sensors, intensity-based POF sensors, multimodal interference-based sensors, Brillouin-frequency-based sensors, and Fabry–Perot cavity sensor. This review aims to highlight areas where further research is required for improving the performance and operating range of POF strain sensors.

Comparative analysis of off-axis digital hologram binarization by error diffusion

Abstract: Digital micromirror device (DMD) provides 2D- and 3D-scenes reconstruction by displaying diffractive and holographic optical elements. The highest frame rates (tens of thousands of Hz) can be achieved if displayed optical elements are binarized. Except DMD applications, hologram binarization is useful for displays creation, image encryption, information compression and storage, fast 3D-printing, etc. Error diffusion is one of the most qualitative implementations of hologram binarization. In this paper, three groups weighting matrices of error diffusion are analyzed: 16 standard, 8 dot and 6 diagonal matrices. Thus, 30 error diffusion methods were used for optically recorded off-axis digital holograms binarization. Quality of image reconstruction from the binarized holograms was compared. Direct applications of error diffusion with large weighting matrices and dot diffusion provide highest reconstruction quality. 7 metrics were used as error diffusion threshold. 12 bypass directions of error diffusion were analyzed. Joint application of Otsu threshold and complex bypass directions allows improving the quality of hologram binarization by 15% additionally.

Novel Optical XOR/OR Logic Gates Based on Topologically Protected Valley Photonic Crystals Edges

Abstract: Valley Photonic Crystals (VPC) have provided a novel topological photonic platform to manipulate light. Here, we construct zigzag and armchair domain walls using two-dimensional silicon VPC, the edges between domains of opposite valley indices link to corresponding topological invariant. We study the light transmission of these edges under defects and sharp bent corners. Based on the Valley-contrasting edges, we design the all-optical logic gates at telecommunication wavelength with XOR/OR function simultaneously. Topologically protected waveguides own high transmission and backscattering-immune features, and coupling of different edge modes result in interference for logic function. Compared with traditional Photonic Crystals logic gates, our device shows outstanding properties including robust transmission, higher contrast ratio and more compact footprint. And it also shows the potential of topological photonics applying in optical logic circuits.

Arbitrary complex retarders using a sequence of spatial light modulators as the basis for adaptive polarisation compensation

Abstract: We show theoretically how a sequence of spatial light modulators (SLMs) can be used to compensate polarisation and phase errors introduced by a spatially variant homogeneous waveplate with any polarisation eigenmode and arbitrary retardance distribution. The resultant compensation is applicable to all pure input polarisation states. The properties of such a system are easily described using Jones calculus in terms of the retardance distribution on each SLM. However, it is not straightforward to determine from the Jones matrices the arrangements nor the settings of each SLM required to implement an arbitrary spatially variant retarder. In order to address this problem, analytic solutions for the required SLM settings are obtained through the construction of a geometrical model on the Poincaré sphere. These solutions are validated against numerical models. These models can be used, for example, to control a multi-pass SLM system acting as the correction device in an efficient vectorial adaptive optics system.

Modelling technique and analysis of porous anti-reflective coatings for reducing wide angle reflectance of thin-film solar cells

Abstract: Bio-inspired anti-reflective (AR) coatings with porous graded refractive index structures are known to considerably reduce the reflectance of light at optical interfaces, however, research is lacking for thin-film cell application. Ray Tracing software coupled with the Effective Medium Theory were used to simulate the reflectance of nanostructured coatings placed above a thin-film system. The most optimal coating was paraboloid-shaped, with 300 nm nipple heights and spacings of 15%. The non-zero refractive index ‘step’ aids light trapping and energy absorption. This coating reduced reflectance in the λ = 300–800 nm range by an average of 2.665% and 11.36% at 0∘ and 80∘ incident light, respectively, whilst increasing annual energy output by 4.39% and 5.39% for standard UK roof and vertical window tilts, respectively. Significant wide angle reflectance capabilities are demonstrated at specifically λ = 300 nm and 80∘ incident light, with a reflectance reduction of 19.192%. There are now many promising manufacturing techniques for these porous nanostructures, such as AR or wavelength filtering coatings for photovoltaics. Further understanding of the exact parameters needed to replicate these nanostructures must be explored to proceed.