Plasmonics最新文献

A D-type photonic crystal fiber (PCF) sensor with ultra-low loss is presented in this paper. The sensor is capable of detecting analytes in the refractive index (RI) range of 1.36 to 1.42. When the RI of the analyte is 1.36, the maximum loss of the sensor in the x-polarized direction is only 23.25 dB/m. A maximum wavelength sensitivity of 8000 nm/RIU is obtained as the analyte has a RI of 1.42, and the sensor has an average wavelength sensitivity of 4678 nm/RIU in the x-polarization direction. The design of the sensor is implemented by coating the side-polished surface of the PCF with a gold film. For the high-sensitivity sensor, the deposition of gold can provide excellent optical performance while maintaining an ultra-low loss. In general, the designed D-type PCF sensor based on side-polished flat gold layer has great potential in various sensing applications due to its ultra-low loss, high sensitivity, and stable properties.

The remarkable optical properties of metallic nanoparticles play a pivotal role in enhancing light absorption for solar energy applications by efficiently converting solar flux into heat. In the pursuit of achieving a broad spectrum absorption from visible to near-infrared (NIR) wavelengths, colloidal nanoparticles, specifically gold/silver hollow nanocubes (HNC) with varied aspect ratios, are utilized. Employing a comprehensive full-wave field analysis, we assess the linear optical characteristics to determine the solar-weighted absorption coefficient of these plasmonic nanofluids across different concentrations and aspect ratios. Our findings reveal that the solar-weighted absorption efficiency of gold hollow plasmonic nanocubes significantly improves (up to 93 %) even at extremely low volume fractions (p = 3.10(^{-6})) compared to silver hollow plasmonic nanocubes (83 %). The outstanding performance of Au hollow plasmonic nanocubes, boasting over 99 % enhancement in solar-weighted absorption efficiency at minimal nanofluid thickness (1.0 cm), underscores their Ag counterparts, marking a significant leap forward in ideal solar absorber conditions.

In the production of alcohol, methanol is produced, and it is toxic to the human body. Methanol poisoning is the biggest cause of the increased death ratio, and it is necessary to control it with fast detection. This study presents a novel design for metal oxide–based alcohol sensors (MOBASs) that achieves exceptional selectivity for methanol detection. The sensor exhibits a remarkably high sensitivity of 2813 nm/RIU for methanol and ethanol within the 1250–1550 nm wavelength range, demonstrating a superior ability to distinguish between these alcohols. Methanol (MeOH) has 99.98% reflection, whereas ethanol (EtOH) gets 68.66%, which makes it more suitable for this sensing application. Other important parameters such as the figure of merit (FOM), quality factor (QF), and detection limit (DL) are 5484.45, 2875.63, and 0.30 × 10⁻⁴ RIU, respectively. By comparing six different structures (D-1 to D-6) of MOBAS, it is easy to identify a good response in terms of transmission.

This paper presents an ultra-narrow band graphene-based surface plasmon resonance refractive index sensor design optimized for enhanced sensing efficiency in biomedical diagnostics and environmental monitoring applications. The proposed sensor architecture leverages a unique combination of circular and triangular resonators strategically patterned to maximize field confinement and sensing performance. Through rigorous electromagnetic simulations using COMSOL Multiphysics software, the sensor parameters are systematically optimized, achieving an exceptional sensitivity of 300 GHzRIU⁻¹ and an average detection accuracy (DA) of 6.494 across all frequency bands. The sensor also exhibits excellent performance metrics, including a high figure of merit (FOM) of 1.948 RIU⁻¹ and a quality factor (Q) ranging from 5.305 to 5.461, demonstrating its potential for accurate detection of minute refractive index variations. Additionally, the study investigates the encoding capabilities of the sensor, showcasing its potential for 2-bit data encoding applications. The synergistic combination of advanced materials and metasurface architecture paves the way for the development of highly sensitive and versatile sensing platforms for various biochemical and environmental sensing applications.

We propose a generalized formula for calculating the dipole polarizability of spherical multilayer nanoshells (MNSs) within the long-wavelength approximation (LWA). Given a MNS with a finite number of concentric layers, radii, and dielectric properties, embedded in a dielectric medium, in the presence of a uniform electric field, we show that its frequency-dependent and complex dipole polarizability can be expressed in terms of the dipole polarizability of the preceding MNS. This approach is different from previous more involved methods where the LWA polarizability of a MNS is usually derived from scattering coefficients. Using both finite-element method- and Mie theory-based simulations, we show that our proposed formula reproduces the usual LWA results, when it is used to predict absorption spectra, by comparing the results to simulated spectra obtained from MNSs with n number of layers up to n = 6 layers. An iterative algorithm for calculating the dipole polarizability of a MNS based on the generalized formula is presented. A Fröhlich function whose zeroes correspond to the dipolar localized surface plasmon resonances (LSPRs) supported by the MNS is proposed. We identify a pairing behaviour by some LSPRs in the Fröhlich function that might also be useful for mode characterization.

In this paper, we propose a tunable surface plasmon resonance (SPR) biosensor using a phase change chalcogenide material (Ge₂Sb₂Te₅) by the transfer matrix method for the detection of human sperm samples. The growing challenge in natural reproduction lies in the heightened infertility of human sperm, attributed to fluctuations in environmental factors. Effectively tackling these concerning aspects requires the utilization of advanced computer-aided devices. However, the precision of such devices, particularly when dealing with low concentrations of sperm, is not meeting the required standards. The proposed SPR biosensor comprises layers of Ag, BaTiO₃, and GST for sperm detection. Achieving tunable and improved refractive index sensing along with a substantial figure of merit (FOM) is accomplished by transitioning the structural phase of GST from amorphous to crystalline. The sensing performances are assessed based on sensitivity, quality factor, detection accuracy, and FOM at a wavelength of 633 nm. The average angular sensitivity achieved is 236 deg/RIU for the crystalline phase and 286 deg/RIU for the amorphous phase, respectively. This sensitivity is observed within the dynamic range of refractive index (RI) spanning from 1.33 to 1.3461 RIU. The performance of our proposed SPR biosensor surpasses that of other reported works.

A two-parameter anti-resonant fiber (ARF) sensor based on the principle of surface plasmon resonance (SPR) is designed to detect refractive index (RI) and temperature simultaneously. Graphene is coated on the externally cut negative curvature tube as the plasmonic medium to excite terahertz SPR for detecting the RI of the external liquid. In addition, polydimethylsiloxane (PDMS) is filled in the graphene-coated tube to sense the temperature of the liquid. The properties of the ARF-SPR sensor are analyzed by the finite element method. The maximum wavelength sensitivity and amplitude sensitivity of 13,888.9 µm/RIU and 87.40 RIU⁻¹ respectively are observed at the second resonance peak for RIs between 1.3 and 1.36, and the minimum resolution is 7.2 × 10⁻⁹ RIU⁻¹. In the temperature range of 26.85 to 76.85 °C, the first resonance peak is insensitive to the temperature, and the maximum temperature sensitivity and amplitude sensitivity of the second resonance peak are 8.4 µm/°C and 0.058 °C⁻¹, respectively, with a resolution on the order of 10⁻⁵. This special design, boasting a simple structure, overcomes the limitations of single-parameter measurements and solves the problems of two-parameter cross-sensitivity while offering excellent sensing performance.

The excitation of surface plasma waves (SPWs) by the interaction of lasers with a metal surface can generate terahertz (THz) radiation at metal-free space interface. We present a novel model for THz radiation generation using two lasers, beating at a metal surface in the presence of a magnetic field. This interaction resonantly excites a SPW, leading to the generation of THz plasmon. Two co-planar lasers having frequency difference of effective electron plasma frequency exert a ponderomotive force to the skin layer of the metal, which induces an oscillatory velocity to the surface electrons and drives the surface plasma waves. The transverse component of the SPW leads to the generation of electromagnetic radiation at THz frequency. Furthermore, the applied external magnetic enhances the transverse current associated with the SPWs. As a result, the THz field strength increased significantly. An expression of THz radiation field is obtained and the field scaling with the magnetic field has been estimated. Our results reported a better THz conversion efficiency for an optimized magnetic field strength. The result of this work delivers a plausible approach to generate THz radiation field from a laser interaction with a metallic surface.

We propose and demonstrate a compact optical fiber temperature sensor based on surface plasmon resonance with high sensitivity and high figure of merit. This optical fiber temperature sensor uses a new photonic crystal fiber designed by us, which is realized by coating a gold film on the polished plane of the photonic crystal fiber and coating the high thermo-optical coefficient material polydimethylsiloxane on the outer surface of the fiber. Small changes in the refractive index of the polydimethylsiloxane due to temperature variations will affect the plasmon pattern, which in turn leads to a change in the measured transmission spectrum. Our numerical results show that the maximum achievable temperature sensitivity of this optical fiber temperature sensor in the range of 60–100 °C is 38 nm/°C, and the maximum refractive index sensitivity and figure of merit are 84444.4 nm/RIU and 603.175 RIU⁻¹, respectively. This is better than the existing various types of PCF temperature sensor. The proposed temperature sensor has the advantages of stable structure, ultra-high temperature sensitivity, and small size. It has good application potential in the field of high-precision temperature control, environmental temperature detecting.

The design of surface plasmon resonance solar absorbers with graphene is demonstrated to study the solar absorbers of photonic devices. With the respective properties of each metal in this structure, the tungsten (W) layer is performed as a ground layer, chromium (Cr) is used to create the resonator design, and the titanium nitride (TiN) substrate layer is constructed between Cr and W layers, respectively. According to the advantages of graphene in making absorbers, a thin film of graphene is also constructed above TiN and below the Cr resonator design. To show the radiation effects in spectrums (between UV and NIR), the four highest wavelength numbers (in micrometers) are picked such as 0.4, 1.6, 1.8, and 2. According to the band range, the output absorption observes 97.2% at 0.7 µm, 95.35% at 1.730 µm, and 90.15% at 2.8 µm, respectively. In solar absorber performing, the first important thing before extracting the absorption rate is design construction, and we presented several stages of outputs for each construction to bring the final (complete) step. After exploring the design and thickness of each existing layer in the design, we can change the below and above parameters of the explored thickness in each layer (resonator, substrate, and ground). The variation can also be demonstrated in respective color plots to show the output radiation in different colors. In the calculating section of the absorption percentage in design, the air mass (AM) and graphene equations are also presented with the explanation of each symbol. The proposed sun-shaped design can be used in performing thermal processes such as water heating systems.