Plasmonics最新文献

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.

In this study we present a novel method for constructing a refractive-index sensor utilizing hybrid modes within a dual ‘Ag-photonic quasi-crystal’ geometry, adhering to the conventional Fibonacci sequence. The reflection spectrum of the geometry demonstrates the presence of three interconnected minima in reflectivity, occurring within the photonic-bandgap of a quasi-crystal. These hybrid modes emerge from the interplay between individual Tamm plasmon mode at the metal-photonic quasi crystal interface and the Fabry–Perot resonant cavity mode formed between two metal layers. The low wavelength dip (Mode-2) and high wavelength dip (Mode-3) display pronounced dispersive characteristics due to the substantial presence of mode-field in the sensing medium. Conversely, the mode situated between them (Mode-1) remains largely unaffected by variations in the refractive index of the sensing layer. Thus, our proposed method offers a wide range of wavelengths linked to Mode 2 and Mode 3, facilitating the concurrent utilization of dual wavelengths for sensor parameter analysis. We investigate the foundational parameters of a bio-photonic sensor, laying the foundation for a dual mode refractive-index sensing mechanism. At a normal angle of incidence, Mode -2 exhibits a maximum sensitivity of 401.4 nm/RIU and a Figure of Merit of 42.8 RIU-1. Meanwhile, for Mode -3, the highest sensitivity and Figure of Merit are 448.87 nm/RIU and 28.89 RIU-1, respectively. Additionally, we propose enhancing the hybrid-mode sensor characteristics by strategically optimizing the photonic quasi-crystal structures to increase the dispersion observed in hybrid Tamm plasmon modes, thus improving sensitivity. Utilization of the dual sensitive mode shows potential for enhancing modern biochemical sensors and optoelectronic devices, with possible applications in detecting diverse blood-related disorders distinguished by refractive index fluctuations in blood components.

Pistacia palaestina (P. palaestina) leaf extract was employed in the synthesis of spherical silver (Ag) nanoparticles, serving as a dual-purpose agent for both reduction and stabilization. These nanoparticles exhibited a range of average sizes between 2 and 27 nm. The size of these nanoparticles was observed to change in response to different concentrations of silver nitrate (AgNO₃). This indicates that an increase in AgNO₃ concentration leads to a reduction in the size of the nanoparticles. The height and morphology were analyzed using scanning probe microscopy (SPM). The crystalline nature of the Ag nanoparticles was confirmed by XRD analysis. Several properties of Ag nanoparticles, including their Raman spectroscopy, UV–visible absorption, and photoluminescence (PL), have been studied. The Raman spectroscopy revealed prominent peaks at 585 cm⁻¹ assigned to skeletal deformation of C-S-C and 1580 cm⁻¹ is linked to symmetric in plane C − C ring stretching. In the UV–visible spectrophotometry analysis, a surface plasmon resonance (SPR) band was observed, ranging between 395 and 398 nm. Additionally, the photoluminescence properties of these nanoparticles were found to vary with the excitation wavelength, marked by a distinct peak at 365 nm, a shoulder peak at 395 nm, and broader peaks observed at 470, 640, 700, and 740 nm. Furthermore, optical analyses of P. palaestina leaf extract indicated the presence of significant active compounds, including polyphenols, glycerol, and chlorophylls.