Optik最新文献

The present research analyze the performance parameters of a surface plasmon resonance (SPR) biosensor such as sensitivity, detection accuracy, quality factor, and combined sensitivity factor as a function of graphene chemical potential in a metal/2D material/graphene multilayer system. The attenuated total reflection of SPR was studied as a function of the number of graphene sheets for different 2D materials (ZnO, MoS${}_2$, MoSe${}_2$, WSe${}_2$, WS${}_2$) and calculated using the transfer matrix method. It was found that there is a critical value of the chemical potential for which the performance parameters change their behavior abruptly for all type of 2D materials used in the biosensor configuration; this chemical potential value is called critical chemical potential. Furthermore, the number of graphene sheets have a strong effect on the performance parameters. Finally, an analytical expression for the sensitivity was deduced, which allows to explain their behavior for the different 2D materials used in the SPR biosensor.

In this manuscript, a photonic crystal fiber (PCF) based sensor working on surface plasmon resonance (SPR) concept, which is polished at both the sides and consisting of semi-circular grooves is presented for the detection of a broad range of analytes with refractive index (RI) from 1.17 to 1.40. Also, the analysis is carried out for the diagnosis of different blood compositions such as water, plasma, white blood cells (WBCs), hemoglobin (HB) and red blood cells (RBCs). Plasmonic material gold is coated in the semi-circular grooves, which causes the strong SPR effect due to reduced distance between core and analyte resulting in excellent detection of the analytes. Thus, the optimum wavelength sensitivity and resolution in the case of broad analyte range detection with RI from 1.17 to 1.40 is obtained as 13000 nm/RIU and 7.7×10⁻⁶ RIU respectively. Also, blood composition detection using the proposed sensor results in excellent sensing performance with the maximum wavelength sensitivity for hemoglobin-RBCs as 11,500 nm/RIU with finer resolution of 8.69×10⁻⁶ RIU.

In this paper, we explored the effect of adding a nanomaterial layer above the add layer on performance parameter of the considered plasmonic structures (conventional, four and five layer SPR sensors). These structures are stimulated by the COMSOL Multiphysics. We have considered LiNbO₃ as an add layer over a thin film of gold. Further, Graphene, Black Phosphorene, Mxene, MoS₂ MoSe_2, WS₂ and WSe₂ as nanomaterial are considered over add-layer. First, we optimised the thickness gold and LiNbO₃. After that, we calculated reflectance and magnetic field dependent performance parameters, i.e., shift in resonance angle (∆θ_r), full beam width (FBW), sensitivity (S), detection accuracy (DA), quality factor (Q. F.), figure of merit (FoM), field intensity at different interfaces (metal-sensing medium (M-S), metal-dielectric (M-D), dielectric-sensing medium (D-S), dielectric-nanomaterial (D-N), nanomaterial-sensing medium (N-S), and penetration depth (PD) for the considered plasmonic structures. The minimum ∆θr is obtained for conventional structure i.e. 1.492° and maximum ∆θr is obtained for WS₂ as nanomaterial used in five layer SPR sensor i.e., 2.052°. Moreover, FBW is also maximum for five layer SPR sensor with WS₂ as nanomaterial i.e., 6.8430°. Moreover, PD has maximum value for conventional SPR sensor i.e., 190.894 nm, 175.94 nm for four layer SPR sensor and less than 175.94 nm for five layer SPR sensor. This comparative study will help to choose add-layer with nanomaterial over add layer and metal thin film layer in a SPR sensor for the detection of analyte or molecules present in the sensing medium.

"In this paper, the optical design of a Three Mirror Anastigmat (TMA) Telescope is modified by substitution of a convex freeform secondary and optimization carried out to obtain improved performance. The proposed convex freeform surface is precisely manufactured using the bonnet polishing technique and tested with a sub-aperture stitched algorithm, meeting the specified surface accuracy requirements. Further, to validate the design, the realized secondary freeform optic is tested in conjunction with primary and tertiary optics in the conceived TMA configuration. The telescope system performance is established using a double-pass interferometric test setup. The modified design enhances the telescope system's performance in the extended field of view (FoV) from ±2.5° to ±3.5° across the track and from ±0.4° to ±0.6° along the track. Measured performance results demonstrate an average modulation transfer function (MTF) of 0.56 and an average Strehl ratio of 0.64 at all field points. The effective focal length of the system is computed to be 975 mm. In summary, the proposed freeform surface significantly improves the optical system performance within the available real estate of the envisaged space telescope system."

The current study describes the effect of changing a shell thickness on photothermal response of a hybrid nanostructures, using theoretical investigation based on the Finite Element Method (FEM) of the COMSOL multi-physics program. The hybrid nanostructures are the Core/Shell nanoparticles (C/S NPs) and the Core/Multi-Shell nanoparticles (C/MS NPs), with fixed core diameter (30 nm) and variable shell thickness (10–20 nm) to create a new type of hybrid nanostructures usable in photonic and optoelectronic applications. For these hybrid nanostructures, gold (Au) and silver (Ag) as a partner of titanium dioxide (TiO₂) were used in thermo-plasmonic part. Hybrid multi-shell nanostructures consist of silver-gold and gold-silver sandwich with titanium dioxide shell in between, all of which are dispersed in an aqueous medium (n = 1.33). The optical properties, the local field distribution, and local heating control of plasmonic nanostructures have been studied under the influence of illumination at plasmonic wavelengths (405, and 532 nm). The results revealed to a clear tunable and adjustable optical and thermo-plasmonic properties by controlling the structure of the core/shell NPs. This results can be enhanced by changing the shell thickness, shape, size, and the nanostructure. The temperature elevation of the core/shell NPs was about 1–5 °C under different wavelengths of laser irradiation. Based on those results, there is possibility of using the core/shell nanoparticles as an efficient heat source in many applications, such as in the sterilization and disinfection of medical equipments.

This study presents a comprehensive experimental investigation conducted on a CIGS-based solar cell incorporating a ZnS buffer layer. The primary objective was to determine key parameters of the CIGS/ZnS heterojunction, including parasitic resistances ($R_s$ and $R_{\mathrm{sh}}$), ideality factor (n), and barrier height (${\varphi }_B$), using experimental current-voltage (I-V) characteristics over a temperature range of 150 K to 300 K under dark conditions. The heterojunction was modelled using a single-diode electrical circuit that accounted for parasitic resistances. Two methods were employed for parameter determination: direct analysis of the (I-V) curves and Cheung's method. Additionally, the charge transport mechanism within the heterojunction is investigated and discussed. Furthermore, the performance of the Al:ZnO/i:ZnO/ZnS/CIGS/Mo solar cell was assessed using the SCAPS-1D simulator, demonstrating an initial solar energy conversion efficiency of 15.01 %. To enhance this efficiency, a hole transport layer (HTL) was integrated between the back electrode and the absorber layer. Extensive studies were conducted to optimize the thickness and doping density of the HTL, including a comparative analysis of different materials used as HTLs. These optimizations resulted in a significant increase in conversion efficiency, reaching up to 28.68 %.

This study investigates the electronic, optical, and thermoelectric properties of lead-free double halide perovskite materials, Rb₂XSbX'₆, through first-principles calculations employing Density Functional Theory (DFT) and the Wien2k code, complemented by Boltzmann transport theory. By substituting X with Ag or Cu and X’ with Cl or Br in Rb₂XSbX’₆, we uncover interesting properties. Rb₂AgSbBr₆, Rb₂AgSbCl_6, Rb₂CuSbCl_6, and Rb₂CuSbBr₆ exhibit low indirect band gaps of 1.18 eV, 2.17 eV, 1.22 eV, and 0.87 eV, respectively, alongside high absorption in the visible region. The studied compounds sustained a high level of structural and thermodynamic stability, which was confirmed by their high bulk modulus and negative formation energy. Furthermore, extensive values were observed for the figure of merit in the thermoelectric study. Given the strong agreement with previous research, these findings position the investigated materials as promising candidates for visible-light solar cell device applications.

Designing metasurfaces is a challenging task. Traditional methodologies, which primarily depend on iterative procedures, are both time-intensive and require specialized expertise. The proposed algorithm uses conditional deep convolutional generative adversarial networks (cDCGAN) to design metasurfaces. This method instantly create a 2D image of a multi-layer metasurface using the scattering parameter $S_{11}$ as the input vector. The algorithm significantly reduces the size of the training dataset by applying pre-training and post-generating steps. The pre-training step involves aliasing and modifying images using a limited color palette. The post-generating step consists of separating the color channels, converting the pixels to vector based images, and fine-tuning the borders. The algorithm is evaluated for three metasurfaces that have unique features compared to the training dataset samples: a single-band metasurface unitcell, a dual-band metasurface unitcell, and a partially trained sample improved by magnetic field analysis. The results show that the proposed algorithm can accurately predict the images of these metasurface unitcells, demonstrating its potential for fast and efficient metasurface design.

Terahertz (THz) imaging is essential for non-contact and non-destructive testing due to its ability to penetrate numerous materials. Typically, the sample is raster-scanned through the beam waist of a confocal optical setup to generate an image in a single-pixel detection scheme. However, the spatial resolution achieved using such imaging configurations remains no less than millimeters, restricting the application of THz imaging. Here in this work, a simple hollow-core metal waveguide (HCMWG) based terahertz imaging setup has been designed and implemented in transmission configuration to record THz hyperspectral images of a sample. The sample is kept in the near-field range of the HCMWG to exploit the THz electric field confinement of the guided mode toward attaining high-resolution imaging. The THz images are acquired by raster scanning the sample in front of the HCMWG output aperture using a single-pixel detection setup. Additionally, spectroscopic sensing using the same setup has been shown by extracting the absorption spectrum of a chemical compound. Further, a plant leaf is used as a sample to demonstrate the applicability of this technique, where the highly resolved transmitted THz image is acquired using the proposed setup. This image is compared with the image recorded using a conventional confocal lens-based THz optical setup. The results show that the technique can resolve subwavelength features (approx. 0.8$\lambda$) of the sample under study while preserving spectroscopic information.

Dispersion-Shifted Fiber (DSF) is essential for reducing chromatic dispersion in high-speed optical communication systems. This study investigates the influence of Four Wave Mixing (FWM) on the quality of signals in orthogonal channels. We examine the advantages of DSF technology and analyze the impact of modulation formats such as On-Off Keying with Return-to-Zero (OOK-RZ) and Duo Binary Modulation class-1 (DBM-1) on transmission performance at different distances. This research assesses the efficacy of orthogonal channels in mitigating four-wave mixing (FWM) effects and improving the overall performance of eight-channel systems at distances of 100 km and 200 km through computer simulations. The results of our study show notable enhancements, namely in optimizing the Q-factor (a metric for signal quality) and reducing bit error rates when employing orthogonal channels compared to previous work. By integrating orthogonal channels with OOK-RZ modulation, we achieved higher performance and reduced nonlinear impairments in a simulated eight-channel system with 50 GHz spacing and 80 Gb/s data rates. This effect was particularly pronounced at high input power levels. At an input power of 20 dBm and a distance of 200 km, this particular combination yielded a maximum Q-factor of 27.25 and a minimum FWM power of −54 dBm. In comparison, under the same conditions, the use of OOK-RZ alone resulted in an FWM power of −24 dBm and a Q-factor of only 1.63. This research provides vital insights into enhancing the efficiency and dependability of optical communication systems, hence facilitating breakthroughs in high-speed data transfer and network scalability.