Plasmonics最新文献

Driven by the growing need for integrated and simultaneous monitoring of multiple physicochemical parameters in complex environments, a polarization-separated multifunctional photonic crystal fiber surface plasmon resonance sensor is proposed and numerically investigated. The proposed sensor integrates polarization multiplexing, in which two orthogonal polarization states are independently excited, with a four-channel independent-groove configuration. Magnetic fluid, seawater, single-stranded deoxyribonucleic acid, and polydimethylsiloxane are selectively filled into four distinct sensing channels, whose surfaces are further modified with gold films and titanium dioxide enhancement layers, allowing parallel detection of magnetic field, salinity, DNA concentration, and temperature. Numerical results show that, over detection ranges of 100–600 Gs for magnetic field intensity, 0-100‰ for salinity, 0.029–0.248 g/cm³ for DNA concentration, and 25–65 °C for temperature, the proposed sensor achieves average sensitivities of 87 pm/Gs, 0.277 nm/‰, 420.55 nm/(g·cm^− 3), and − 2.26 nm/°C, respectively. Benefiting from the polarization-separation mechanism and multichannel sensing architecture, the proposed sensor exhibits high integration, high sensitivity, and simultaneous multiparameter sensing capability. These advantages make it a promising fiber-optic sensing platform for complex application scenarios, including marine environmental monitoring, biomedical analysis, and electrochemical sensing.

This study develops a Transition-Resolved Renormalization Framework for separating intrinsic excitonic structure from environment-induced electrodynamic effects in hybrid nanocrystal–plasmonic systems. TD-DFT results for CdSe–ZnS and published atomistic-pseudopotential data for an InP reference system are used as independent electronic-structure inputs. For CdSe–ZnS, four resolved bands exhibit a common displacement of 13.8 ± 1.0 nm, corresponding to an effective mean energy correction of 64 ± 11 meV. Independently, the developed interface relation yields 63.44 meV at the nominal emitter–surface separation (:dapprox:4.0) nm, equivalent to 13.99 nm, using TD-DFT transition moments, dielectric screening, the frequency-dependent Au response, and the structurally constrained emitter–surface separation. This close agreement provides reproducible electrodynamic validation of the observed spectral renormalization. The calculated correction is then transferred, without transition-specific refitting, to a five-transition InP reference hierarchy, producing conditional renormalized predictions while preserving transition ordering. A lifetime consistency check for the conventional 660 nm CdSe–ZnS band gives a calculated quartz lifetime of 19.35 ns, close to the measured value of approximately 20 ns. Combining this calculated lifetime with the experimentally measured quartz-to-Au decay-rate enhancement yields 6.77 ns near Au, consistent with the measured value of approximately 7 ns. The corresponding Au-induced decay-rate factor of 2.86 is subsequently used to predict lifetimes for the four higher-energy transitions.

Terahertz (THz) plasmonic tunability is a key requirement for the practical realization of next-generation, ultrafast, and compact plasmonic platforms for sensing, communication, waveguiding, and spectroscopic applications. This study addresses the challenge of weak field confinement commonly observed in metallic plasmonic waveguides by introducing indium antimonide (InSb) as the core material of a cylindrical waveguide operating in the THz regime. Due to its strong THz response and temperature-dependent electronic properties, InSb provides an effective and practically feasible approach for enhancing plasmonic confinement. The effects of temperature variation, along with the influence of core and cladding parameters, on the propagation constant (β), normalized phase velocity (vₚ/c), and effective mode index (n_eff) are systematically analyzed. Numerical results are presented for dispersion characteristics, propagation bands, attenuation, cut off frequencies, effective mode index, field distributions, and phase velocity in both the insulating (T = 200 K) and metallic (T = 300 K) phases of InSb. Additionally, the impact of waveguide radius and operating temperature on supported plasmonic modes is investigated. The results demonstrate that substantial control over propagation behavior such as plasmonic confinement, propagation band gaps, and optical–acoustic mode hybridization, can be achieved through combined structural engineering and temperature tuning. This reversible tunability enables the realization of temperature-controlled plasmonic waveguides suitable for THz modulators, switches, and sensing devices.

This study aimed to evaluate the antibacterial activity of PLAL-synthesized gold nanoparticles (AuNPs) against environmentally isolated waterborne pathogens. AuNPs were successfully synthesized via a green pulsed laser ablation in liquid (PLAL) technique, offering a clean and chemical-free route for nanomaterial production. Structural and morphological analyses confirmed the formation of crystalline, well-dispersed AuNPs with an average size of ~ 47 nm, while zeta potential measurements (− 39 mV) demonstrated excellent colloidal stability. The antibacterial performance of AuNPs was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, revealing a clear concentration-dependent response. The inhibition zone increased from ~ 6 mm (control) to ~ 18 mm at the highest concentration, with S. aureus exhibiting the highest susceptibility. The superior antibacterial activity is attributed to the synergistic effects of nanoscale size, high surface reactivity, and strong dispersion stability, which enhance nanoparticle–cell interactions and induce cellular damage. The inhibition zone increased from 6.04 ± 0.10 mm in the control group to 18.10 ± 0.46 mm at the highest AuNP concentration of 3.1 mg/L, demonstrating strong concentration-dependent antibacterial activity.

High performance label free localized surface plasmon resonance (LSPR) sensors require resonances that are both sensitive to refractive-index changes and sufficiently narrow for reliable spectral tracking. In this work, a diamond-core/silver-shell nanorod is investigated as a compact refractive-index sensor using three-dimensional finite-element simulations. The nanorod length (L=30text {--}70~textrm{nm}), core radius (r=4text {--}12~textrm{nm}), and silver-shell thickness (t=4text {--}12~textrm{nm}) are varied for surrounding refractive indices of (n_textrm{env}=1.33text {--}1.45), with wavelength-dependent optical constants assigned to both diamond and silver. All three geometry sweeps demonstrate nearly linear red shifts of the longitudinal plasmon resonance with increasing (n_textrm{env}). Increasing the nanorod length raises the bulk sensitivity from (175) to (400~mathrm {nm/RIU}), whereas the best length-dependent average figure of merit (FOM) occurs at (L=60~textrm{nm}) because further elongation broadens the resonance. Reducing the core radius improves environmental coupling, giving (400~mathrm {nm/RIU}) for (r=4text {--}6~textrm{nm}). In the shell-thickness sweep, (t=4~textrm{nm}) provides the best sensitivity–linewidth balance, with (375~mathrm {nm/RIU}) and an average FOM of (21.47). For the representative high-response geometry (L=70~textrm{nm}), (r=4~textrm{nm}), and (t=4~textrm{nm}), the normalized field map at (n_textrm{env}=1.33) and (lambda =498~textrm{nm}) shows end-cap hotspots with (|E|/|E_0|approx 18.4). In this work, absorption cross-section is measured in sqaure meter. Within the smooth-interface classical finite-element model used here, long, slender diamond cores with thin silver coatings give the strongest refractive-index response in the investigated parameter range. Experimental realization, however, will require careful control of silver-shell continuity, roughness, oxidation, and size-dependent damping.

Reliable and quick coronavirus detection is still necessary for the efficient disease monitoring and public safety. This work proposes an extremely sensitive sensor based on surface plasmon resonance (SPR) technique for SARS-CoV-2 detection using an NSG prism/silver (Ag)/gallium nitride (GaN)/barium titanate (BaTiO₃) multilayered structure. The addition of GaN as a large band gap material improve the sensing performance which further increases the interaction with the sensing medium of the evanescent field. The transfer matrix approach (TMA) is used to examine the sensing mechanism with the 633 nm wavelength. Further, the Taguchi optimization approach is used to identify the ideal thicknesses of the Ag, GaN, and BaTiO₃ layers in order to further enhance sensor functionality. In this, the impact of layers thickness variation on important performance metrics, including as full width at half maximum (FWHM) is thoroughly assessed using an L9 Taguchi array. The most important design factors influencing sensor response are found using analysis of variance (ANOVA) method and Taguchi signal-to-noise ratio (SNR) assessment. Here, the Taguchi SNR is utilized as a statistical optimization indicator to determine the optimal design parameters for minimizing the FWHM based on the ‘smaller is better’ criterion. Higher resonance angle shifting and better sensing performances are observed by this optimized sensor design. Further, the findings show that the combination of this optimization with GaN integration offers a potential foundation for the creation of highly effective SPR sensor structure for SARS-CoV-19 detection. Hence, this suggested method provides insightful information for the development of novel plasmonic sensors for monitoring pathogens and clinical diagnosis.

In this paper, the plasmonic directional couplers (PDCs) are studied as key elements of nanophotonics circuits because of their potential applications for achieving strong light-matter interactions and subwavelength optical confinement, along with small size and compactness for on-chip applications. In the last two decades, three major types of PDCs have been identified according to the classification of these designs: plasmonic couplers in conventional platforms, hybrid systems, and periodic couplers. This paper discusses the functioning of PDCs based on numerical and experimental studies and describes them using the methods of coupled-mode theory and supermodes analysis. Typical Metal-Insulator- Metal (MIM) couplers allow for an extremely small size but suffer from inherent ohmic loss effects. Hybrid dielectric-plasmonic structures provide improved waveguiding properties along with larger bandwidths. The implementation of tapered-funnel, triangular, semi-elliptic, and oblique slits designs has resulted in significantly reduced impedance misalignment and provided coupler efficiencies exceeding 90%. Furthermore, Advanced materials such as graphene and ferroelectric films (barium titanate, lead zirconate titanate, and lithium niobate) offer tuning and electro-optic modulating ability needed for future photonic integrated circuits. Moreover, new uses of quantum dot-plasmonic complexes (PDCs) in quantum Plasmonics, optical switches, biosensors, and all-optical logic devices are described in the document. Finally, approaches to the development of high-speed optical and terahertz interconnects are covered, involving topological Plasmonic and integration on CMOS substrates.

In this paper, the design and optimization of a dual-band THz biosensor employing a perfect metamaterial absorber (PMA) is presented. The proposed PMA configuration is evolved from a ring resonator connected to a central metallic patch through a set of connecting stub lines, thereby enhancing the effective current path and enabling structural miniaturization. The graphene-based resonator, realized on a Gallium Arsenide (GaAs) substrate, exhibits dual resonance characteristics centred at 2.5 THz and 3.0 THz with near-unity absorptivity at both operating frequencies. The proposed unit cell has a footprint of 0.25λ × 0.25λ at the lowest operating frequency, making it suitable for compact THz sensing applications. Owing to its geometrically symmetric configuration, the proposed absorber exhibits polarization-insensitive characteristics and maintains 80% absorption performance for oblique incidence angles up to 70°. To achieve rapid convergence and efficient optimization of the geometrical parameters, the proposed structure is optimized using the metaheuristic Marine Predators Algorithm (MPA). The optimization framework demonstrates good optimization accuracy with a mean squared error (MSE) below 0.1 and a mean absolute percentage error (MAPE) below 1% in comparison with traditional inbuilt optimizers in the electromagnetic solver. The suitability of the proposed THz PMA for biomedical sensing applications is investigated through refractive index-based analyte characterization. Theoretical analysis show that the PMA based biosensor offers sensitivities of 498 and 396 GHz/RIU at 2.5 and 3.0 THz, respectively thereby demonstrating the robustness of the proposed biosensing platform for advanced biomedical detection applications.

In biomedical diagnostics, the detection and analysis of biological components are extremely important for the identification of biomarkers related to disease diagnosis, monitoring of cellular processes, diagnosis of neurological and hematological disorders. Accurate sensing of these biological materials can be very useful in the investigation of disease progression, cellular analysis, and physiological functions. This research work demonstrated a refractive index sensor in the infrared region utilizing for detection of biological materials. The simulation results exhibit single resonance mode achieving absorption rate greater than 99%, located at 4.525 μm wavelength. Furthermore, evaluating the sensor performance by observing changes in the resonance peak due to variations in the refractive index of the surrounding medium. The proposed sensor displays high Q-factor, sensitivity and figure of merit with maximum values are 150.8, 1.47 μm /RIU and 49 RIU^-1 with refractive index range from 1 to 1.5. This outstanding sensitivity makes the sensor highly effective for detection of various types of biological constituents including next-generation biomedical diagnostics, personalized medicine, and clinical research.

A simple-structured hollow-core anti-resonant fiber (HC-ARF) polarization filter based on the surface plasmon resonance (SPR) effect is proposed. The polarization filter adopts fused silica as the substrate material and features a symmetric six-tube cladding structure. The gold films are deposited on the inner surface of the anti-resonant tubes along the x-direction to excite the SPR, while the nested anti-resonant tubes are introduced in the y direction to suppress the leakage loss of the y-polarized mode. The full-vector finite element method (FV-FEM) is used to systematically investigate the influence of core diameter, resonant tube inner diameter, nested tube inner diameter, gold film thickness and device length on the filtering performance. The results demonstrate that, under the optimized structural parameters, the polarization filter achieves a maximum polarization extinction ratio (PER) of -435 dB (-239 dB at 1.55 μm). It offers a bandwidth of 353 nm (1391 nm to 1481 nm and from 1518 nm to 1781 nm, which covers all the commonly used communication bands. The proposed filter features a simple structure and exhibits broad bandwidth and high PER performance, showing promising application prospects in the all-optical communication, optical fiber sensing and the other related fields.