Results in Optics最新文献

An accurate and efficient semi-vectorial mode solver, examining Electric (E) and Magnetic (H) fields, is utilized to explore the communication characteristics of various slab waveguides. This approach relies on the Finite Difference Method (FDM) using uniform grid points, employing a Higher (Fourth) Order Compact type technique coupled with Conjugate Gradient (CG) iteration. The present study is an extension of the previous work where various aspects of E- and H-field propagations through rib-strucured waveguide was analyzed successfully. By incorporating the refractive index profile of the slab structure, excellent functionality of the waveguide is demonstrated here in Electric field by utilizing the concepts of normalized index and effective or modal index, confinement factor, and the modal birefringence properties which proves to be critical for potential applications in photonic integrated circuits. The materials chosen for the purpose are AlGaAs-GaAs and GeSi which play a vital role in characterizing the waveguides’performances through simulation using MATLAB. The use of surface and contour plots aids in visualizing the distribution of corresponding field within the guided modes. This analysis significantly contributes in understanding the waveguide's behavior and confinement capability during the field propagation. Most importantly, the variations of the waveguides’performance indices with their structure parameters help to identify their optimized values for fabrication to enhance the transmission efficiency of the waveguide.

In this study, the sol–gel method was used to synthesize calcium titanate (CaTiO₃) at different calcination temperatures (400–800 °C). The main objective of this work is to find, using various characterization techniques, how the calcination temperature influences the optical, structural, and photocatalytic properties of CaTiO₃. According to the DTA/TGA analysis, 600 °C was the ideal calcination temperature for the synthesis of CaTiO₃ nanoparticles. The photocatalytic treatment of simulated wastewater demonstrates its potential application in wastewater treatment. For all calcination temperatures, the percentage of Chemical Oxygen Demand (COD) removed after treatment was 100 % for the initial COD of 700 mg/L, more than 83 % for the initial COD of 5000 mg/L, and more than 71 % for the initial COD of 16000 mg/l.

In the present work, one-step, mass-scale productive solid state reaction method has been employed for the preparation of gadolinium (Gd) doped ZnO (GZO_x: x  = 0, 2, 4, 6, 8 wt%) nanostructures. The prepared GZO_x samples have been studies their structural, morphological, elemental diffusion profile and optical properties using P-XRD, FE-SEM, EDS, FTIR, and photoluminescence (PL) spectroscopy. The powder X-ray diffractometer (P-XRD) results clearly indicate strong and sharp diffraction peaks with broadening that confirms the formation of hexagonal nanocrystalline structure of ZnO and Gd doped ZnO. The hexagonal morphology formation of the grains after doping of Gd contents into the ZnO nanostructures system is seen from the FE-SEM micrographs and the sizes of the grains are found to close to the results obtained from XRD patterns. The presence of Gd contents in ZnO matrix confirms its doping by EDS spectrum of 4 wt% Gd doped ZnO nanostructures. Fourier transform infrared (FTIR) results confirm the presence of functional groups and chemical bonding of ZnO at room temperature. Investigation of optical emission is interesting and the PL spectra reveal two emission peaks, one in UV-region located in the range of ∼385 to 395 nm and other is defects related emission centred at ∼450, ∼468, ∼503 and ∼562 nm in visible region for all the samples. The enhanced PL intensity is observed in the higher doped Gd contents in ZnO nanostructures and can be attributed to the presence of Gd ions into ZnO lattice. The detailed structural and luminescence analysis has been carried out and correlated. The study of structural and optical properties GZO_x samples suggest the luminescent optoelectronic applications.

Light fidelity (LiFi) is one of the most promising areas within wireless optical communication system. It provides many benefits, including high capacity, improved security and enhanced cost-effectiveness. However, there is still challenges which are link blockages, attenuation, interference and bandwidth restriction of modulation techniques. Orthogonal space–time block coding (OSTBC) offers a suitable solution to address link blockage by providing an alternative communication channel between the transmitter and the receiver. OSTBC has more tolerate to the practical channel impact limitation such as attenuation and interference that may occur in overlapping regions. In addition, the use of the OSTBC technique enhances the system’s ability to transfer data as the transmission rate is duplicated by the number of transmitters and receivers. This paper proposes the utilisation of a LiFi transceiver-based OSTBC that employs quadrature amplitude modulation (QAM) in conjunction with orthogonal frequency-division multiplexing (OFDM). Co-simulation tools have been done by integrated Matlab with Optisystem, were used in the design of LiFi transceiver with all assumption required. The findings reveal the capability of LiFi transceiver of transmitting rate up to 15 Gbps with maintaining a satisfactory bit error rate (BER) of 10⁻⁴ over a link range of 200 m even in the presence of realistic channel effects. Moreover, the LiFi transceiver’s structure used does not incorporate optical amplifier components, resulting in reduced computational complexity compared to conventional LiFi transceivers. The proposed system proved its progress over the previous work under the influence of the same input effects.

This study explores how various surfactants (CTAB, PVA, and SLS) affect the properties of SnO₂ nanoparticles synthesized via co-precipitation. The impact of these surfactants on crystal structure, microstructure, and bandgap characteristics was analyzed using XRD, FE-SEM, FTIR, UV–Vis-NIR, and PL spectroscopy techniques. The phase purity was assessed using X-ray powder diffraction and Fourier-transform infrared spectroscopy (FTIR), confirming a tetragonal rutile crystal structure (P4₂/mnm (1 3 6) space group). The crystalline size was determined via Scherer and Williamson-Hall techniques. FTIR analysis identified Sn-O vibrational modes and other functional groups. Scanning electron microscopy (SEM) revealed spherical-shaped particles with a flake-like grain structure, matching the crystalline size distribution. UV–Vis absorption spectroscopy explored optical properties, determining absorbance and optical bandgap using Tauc's plot. Photoluminescence (PL) response was observed under 248 nm illumination, showing peaks (363.6–558.6 nm) attributed to near band edge emission and defect energy levels from Sn interstitials and oxygen vacancies. CIE parameters, including color coordinates (x, y), color-correlated temperature of SnO₂ nanoparticles. This study provides valuable insights into the potential applications of pure and surfactant-assisted SnO₂ nanoparticles in optoelectronics.

This study presents a comparison between spin-coating, dip-coating, and drop-coating that entails investigating the effect of the thickness on P3HT thin film properties. The grown P3HT thin films were characterized using a range of analytical techniques to evaluate their structural, morphological and optical properties. The XRD of P3HT thin films revealed strong thickness dependence where 30 nm thin film had low diffraction intensity and 148 nm thin film revealed the highest intensity. The nanoball morphology which varies in terms of distribution and clustering based on deposition method was attained. From the FTIR measurements, we observed no noticeable change in vibrational frequencies regardless of the deposition method and the thin film thickness. The abnormalities in absorption measurements suggest thickness dependence due to various deposition methods that resulted in oxygen defect-related states that modified the energy band gap. From PL analysis we observed an increase in the emission intensity following the increase in thin film thickness which denotes the change in P3HT conformation as the number of defects increases. Thus, the drop-coating method produced a thicker thin film that revealed outstanding structural and optical properties that are vital for organic photovoltaic (OPV) device functioning. Even though the drop-coating method produced thin films with promising results for OPV devices, it lacks in terms of reproducibility such as controlling thin film thickness which causes extrinsic degradation effects. Thus, the spin-coating method is viable as one can control spin speed to attain the desired thickness for optimum performance of P3HT in OPV devices.

This paper presents the surface plasmon resonance (SPR) characteristics of D-shaped silica multimode optical fiber coated with bilayer silver-gold film. The effect of various coating thicknesses on the SPR characteristics was investigated through simulation using COMSOL Multiphysics. The inner layer Ag thickness varied from 20 nm to 60 nm, and the outer layer Au thickness ranged from 5 nm to 25 nm. Prior simulation results indicated that a single-layer silver (Ag) coating produces a narrower plasmonic curve than a single-layer gold (Au) coating. The confinement loss and the resonance wavelengths were simulated for the sensing medium with a refractive index (RI) range of 1.40–1.45. The simulation results show that the Ag/Au bilayers coated sensors have better full-width-half-maximum (FWHM) and figure-of-merit (FOM) than the single-layer coated sensors. The Ag/Au with a 40 nm/5 nm thickness exhibits the highest confinement loss, with a wavelength sensitivity of 10 000 nm/RIU and a figure-of-merit (FOM) of 500 RIU⁻¹. The proposed sensor using a D-shaped optical fiber coated with Ag/Au layers has a high potential for remote sensing applications involving chemical liquids, offering robust and accurate measurements within the tested refractive index range.

In organic bulk heterojunction solar cells, the internal quantum efficiency can be considered as the product of the absorption efficiency, the exciton diffusion efficiency, the charge transfer efficiency, and the charge collection efficiency. In previous studies, it has been reported that charge transfer and charge collection is very high in these solar cells, approaching 100 %. With a Monte Carlo simulation approach that considers the hopping of charges within the two materials of the heterojunctions, it is highlighted that an estimate of the charge collection efficiency can be evaluated considering that a certain number of charges do not reach the electrodes because of the random arrangement of the two materials in the heterojunction. The case of P3HT:PCBM (1:1 ratio) has been analyzed in this study.

The reported power conversion efficiency (PCE) of single-junction perovskite solar cells (PSCs) has increased rapidly to over 26 %. Promoting the PSC’s device performance to approach its fundamental efficiency limit of over 30 % requires mitigating optical and recombination losses. In this work, we examine the performance of MAPbI₃-based inverted p-i-n PSCs with the aid of a numerical device simulator (OghmaNano version 8.0.038). The simulator considers the thickness and charge carrier mobilities of the device’s photoactive layer and band-to-band recombination of the PSC devices. We reveal that maximum efficiency as high as 28.4 % can be expected for optimized single-junction MAPbI₃-based PSC with an active layer thickness of 950 nm, charge carrier mobility of 71 cm²V⁻¹s⁻¹ and a recombination rate constant <1 × 10⁻¹¹ cm³s⁻¹. However, the simulated efficiency is still below the fundamental efficiency limit as we assume a flat device that allows optical loss from reflection. Therefore, we introduce single and double layers of anti-reflective coatings (SL-ARC and DL-ARC) to enhance the PV performance further. It was found that the inclusion of PMMA-based SL-ARC with a thickness of 70 nm could push the PCE values up to 29.7 %. By inserting another layer of ARC with a lower refractive index after the PMMA layer, we could further push the PCE. As a result, the PMMA/PDMS DL-ARC −based PSCs are predicted to have a PCE of 30.25 %. Our work showcases guidelines for designing inverted perovskite solar cells with efficiency near its fundamental limit.

The phenomenon of extraordinary transmission (EOT) through perforated metal sheets (hole arrays) has been an interesting field of research since its discovery due to its potential applications. In this paper, we focus on the excitation of multiple surface plasmon resonance (SPR) modes in a complex rectangular hole array-based unit cell. This unit cell configuration consists of two horizontally placed holes with a vertical hole placed between them in a near-field electromagnetic coupling regime. We demonstrate, tailoring the SPR resonances along with the Q factor by altering the relative positions among the rectangular holes. Generally, when the excitation field is applied along the longer side of the rectangular hole, no surface plasmon resonance (SPR) is observed. However, in this work, we have shown excitation of SPR modes through near-field interactions even in the case of probe field being applied along the longer side. In such cases, significant modifications in resonance Q-factors are observed which is attributed to near-field interactions among the rectangular holes. Furthermore, our investigation explores the hybridization of (1,0) peaks within the multiple-hole arrays due to the different effective periodicities. Our work also demonstrates a route to excite and tune SPR modes without altering the unit cell periodicity, hence can provide an additional degree of freedom in SPR excitations.