Results in Optics最新文献

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.

The laws of interaction of electromagnetic wave radiation with pyridine molecules and atoms were studied using Raman light scattering spectra of light, and it was shown that the spectra appearing in the lower frequency range (0 ÷ 1031 cm⁻¹) are related to the rotational-rocking movement of molecules. Based on quantum-chemical calculations, a structural model of the pyridine molecule was created. The possibility of determining the bond lengths and angles between the atoms in the pyridine molecule was suggested. Based on the obtained results, the frequency values of the Raman scattering spectra of light from the pyridine molecule were determined by theoretical calculations and compared with the experimental results. Based on the analysis of the results of the research, it was found that the intensity of the Raman scattering spectrum of the light generated by the rotational-rocking laws of the pyridine molecule is significantly smaller than the intensity of the spectra corresponding to other frequencies.

Fluoro-perovskite compounds are important and auspicious materials according to their properties in photovoltaic anti-reflective coating and optoelectronics. In this study, the structural, mechanical, and optoelectronic properties of Cesium Lead Fluoride CsPbF₃ were investigated using first principle calculations with generalized gradient approximations. The effect of stress on the crystal structure of CsPbF₃ was examined at 0, 20, 40, and 59 GPa. It was found that the lattice constant is decreased with increasing stress, and the elastic, electronic, and optical properties of the material were significantly affected. The density of states and band gap of CsPbF₃ were also calculated, and the band gap was found to be zero at 59 GPa. The cubical structure of CsPbF₃ is distorted at 58 GPa. The various mechanical characteristics such as the bulk modulus, shear modulus, Young’s modulus, and Poisson ratio were derived and discussed. The results indicate that CsPbF₃ exhibits ductile behaviour and anisotropic nature under stress, and the increase in refractive index, absorption, reflectivity, and conductivity at high stress make it a promising material for optoelectronic devices.

In this article, an incoherent beam combination of higher-order Gaussian beams through atmospheric turbulence is studied. An analytical expression of the combined intensity and spot size of higher-order Gaussian beams such as Hermite Gaussian (HG), Laguerre Gaussian (LG), and Bessel Gaussian (BG) are derived. The performance of these higher-order Gaussian beams is analyzed in various modes including the effect of beam wander, jitter, bore-sight error, Strehl ratio, and Visibility. A series of analytical simulations shows the intensity variation of 19 higher-order combined beams. Spot size, peak, and average intensity comparisons are made between various modes of higher-order Gaussian beam combinations. It is seen that the spot size of the combined beam increases rapidly in a higher mode of HG and LG beam. We evaluate the efficiency of combining beams at different distances, noting that it increases with higher mode orders and reaches its maximum with the $H{G}_{22}$ mode. Additionally, we explore the performance of higher-order Gaussian beam combinations under varying ground turbulence conditions. We observe that higher modes such as $H{G}_{22}$ and $L{G}_{22}$ are more susceptible to strong turbulence compared to lower modes.