Search Results (542)

To obtain a flat top shaped passband in a conventional thin-film-based optical bandpass filter (OBF), it needs a large number of constitutional layers of thin films, which makes the film deposition systems more complicated and accumulates errors in film growth. A flat top and polarization-independent optical bandpass filter structure is proposed based on experimentally verified polarization independency in the form of a prism-pair coupled planar optical waveguide (POW). The POW is composed of two waveguide stacks, which consists of nine planar thin-film layers. Theoretical simulations show that the flat band top spans about 5 nm with transmittance over 97.8%. The passband is designed to be centered at 632.8 nm, the He-Ne laser wavelength, and the FWHM (full width at half maximum) bandwidth is about 35 nm. Within 0.5° tuning for the incident angle of the light, the passband could be shifted within 50 nm, while its transmittance fluctuates only less than 1% and the passband shape distorts only slightly. This type of OBF is potentially applicable in various fields of optical and laser spectroscopies. Full article

In this study, a terahertz microfluidic multi-band sensor was designed. Unlike previous microfluidic absorption sensors that rely on dipole resonance, the proposed sensor uses a physical mechanism for absorption by exciting higher-order lattice resonances in microfluidic structures. With a Fabry–Perot cavity, the sensor can form an absorption peak with a high quality factor (Q) and narrow full width at half maximum (FWHM). A high Q value and a narrow FWHM are valuable in the field of sensing and provide strong support for high-precision sensing. On this basis, the sensing performance of the device was investigated. The simulation results clearly show that the absorption sensor has ultra-high sensitivity, which reaches 400 GHz/Refractive Index Unit (RIU). In addition, the sensor generates three absorption peaks, overcoming the limitations of a single frequency band in a composite resonance mode and multidimensional frequency response, which has potential application value in the field of volatile organic compound (VOC) sensing. Full article

Previous investigations devoted to non-spherical nanoparticles for biosensing have primarily addressed two hot topics, namely, finding nanoparticles with the best shape for refractive index sensing properties and the optimization of size parameters. In this study, based on these hot topics, Au-Ag alloy nanoparticles with excellent optical properties were selected as the research object. Targeting rotationally symmetric Au-Ag alloy nanoparticles for biosensing applications, the complex media function correction model and T-matrix approach were used to systematically analyze the variation patterns of extinction properties, refractive index sensitivity, full width at half maximum, and figure of merit of three rotationally symmetric Au-Ag alloy nanoparticles with respect to the size of the particles and the Au molar fraction. In addition, we optimized the figure of merit to obtain the best size parameters and Au molar fractions for the three rotationally symmetric Au-Ag alloy nanoparticles. Finally, the range of dimensional parameters corresponding to a figure of merit greater than 98% of its maximum value was calculated. The results show that the optimized Au-Ag alloy nanorods exhibit a refractive index sensitivity of 395.2 nm/RIU, a figure of merit of 7.16, and a wide range of size parameters. Therefore, the optimized Au-Ag alloy nanorods can be used as high-performance biosensors. Furthermore, this study provides theoretical guidance for the application and preparation of rotationally symmetric Au-Ag alloy nanoparticles in biosensing. Full article

This paper investigates the effect of plasticity ball burnishing on characteristics of surface integrity, residual stress and hardness of laser direct energy deposited (DEDed) Stellite 21 alloys, with a focus on the burnishing directional effect on surface and microstructural deformation. The results demonstrated that the burnishing improved surface finish, reducing Sa and Sz by 24% and 47%, respectively. The burnishing flattened and modified the cellular/columnar grains at a depth of 50 µm, with the most notable changes observed on the cross-sectional plane normal to the burnishing direction. Compared to the ground surface, the burnishing introduced higher and deeper compressive stresses along normal to the burnishing/grinding direction (−1341 MPa and 61 µm) as compared to that along the burnishing direction (−449 MPa and 56 µm). Likewise, the burnishing increased the full width at half maximum (FWHM) in the same fashion by broadening XRD peaks along normal to the burnishing direction. Due to higher grain modification and dislocation density, the burnishing has improved microhardness at a depth of 320 µm by 26% along normal to the burnishing direction. These findings demonstrate that the plasticity ball burnishing has a directional effect on plastic deformation and can be considered a plausible technique for tailored surface integrity, residual stress and hardness, which potentially improve the service performance of DEDed Stellite 21 alloy components. Full article

This work presents a novel $C{O}_2$ gas sensor based on a slotted polymer-phaseshift Bragg grating (SP-PSBG) waveguide filled with polyhexamethylene biguanide (PHMB) as the sensing medium. The transmission resonance, characterized by a narrow peak with a full width at half maximum (FWHM) of 1.6 nm within the Bragg grating bandgap, is highly responsive to refractive index changes in PHMB caused by variations in $C{O}_2$ concentration. Numerical simulations demonstrate a sensitivity of 14.4 pm/ppm, outperforming conventional gas sensors based on functional material coatings. This enhanced performance comes from the direct interaction between the PHMB-filled resonant structure and the cladding that contains $C{O}_2$ molecules, eliminating the need for polymer-coated cladding layers. The optimization approach employed in this design focuses on maximizing the optical confinement factor within the PHMB-filled slot, leading to an effective overlap between the guided optical mode and the sensing material. Full article

This study addresses the challenges of high-power consumption and complexity in conventional infrared (IR) gas sensors by integrating metamaterials and gold coatings into IR radiation sources to reduce radiation loss. In addition, emitter design optimization and material selection were employed to minimize conduction loss. Our metasurface exhibited superior performance, achieving a narrower full width at half maximum at 4197 and 3950 nm, resulting in more confined emission spectral ranges. This focused emission reduced energy waste at unnecessary wavelengths, improving efficiency compared to traditional blackbody emitters. At 300 °C, the device consumed only 6.8 mW, while maintaining temperature uniformity and a fast response time. This enhancement is promising for the operation of such sensors in IoT networks with ultra-low power consumption and at suitably low costs for widespread demands in high-technology farming. Full article

Wideband electromagnetic pulse detection is a crucial method for lightning disaster monitoring. However, the random nature of lightning events presents challenges in fulfilling real-time calibration requirements for electromagnetic pulse sensors. This paper introduces a segmented ultra-wideband TEM horn antenna tailored for portable calibration experiments in electromagnetic pulse detection systems. The radiating plates feature a four-section polygonal design, and an end-loaded metal plate is integrated to reduce reflection signal interference. Rigorous simulation analyses were performed on three key factors impacting antenna radiation performance: aperture impedance, tapering profile, and end loading configuration. Experimental results show that the designed antenna achieves a peak field strength of 48.9 V/m at a 10 m distance, with a rise time of 0.87 ns and a full width at half maximum of 1.75 ns. The operating frequency ranges from 48 MHz to 150 MHz, with main lobe beamwidths of 43° and 83° in the E-plane and H-plane radiation patterns, respectively. These parameters meet the technical requirements for electromagnetic pulse sensor calibration experiments. Full article

The degenerate optical parametric oscillator (OPO) is demonstrated to generate high-power, broadband mid-infrared MgO-doped periodically poled lithium niobate (MgO:PPLN) femtosecond laser at 151 MHz, synchronously pumped by a commercial Kerr-lens mode-locked Yb:KGW oscillator at 1028 nm. The average power of the degenerate OPO centered at 2056 nm is as high as 740 mW, which is the highest output power from a reported 2 μm degenerate femtosecond OPO, pumped by a bulk solid-state laser. The full width at half maximum (FWHM) spectral bandwidth of the degenerate OPO is 87.4 nm, corresponding to a theoretical, Fourier-limited pulse duration of 51 fs. These remarkable results indicate that degenerate OPO is a great potential candidate technology for generating high-power and few-cycle femtosecond pulses around 2 μm. Such mid-infrared sources are well-suited for high harmonic generation, a pumping source for mid- to far-infrared OPO. Full article

This study is a comprehensive experimental and computational investigation into high-resolution laser beam diagnostics, combining classical statistical techniques, numerical image processing, and machine learning-based predictive modeling. A dataset of 50 sequential beam profile images was collected from a femtosecond fiber laser operating at a central wavelength of 780 nm with a pulse duration of approximately 125 fs. These images were analyzed to extract spatial and temporal beam characteristics, including centroid displacement, Full Width at Half Maximum (FWHM), ellipticity ratio, and an asymmetry index. All parameters were derived using intensity-weighted algorithms and directional cross-sectional analysis to ensure accurate and consistent quantification of the beam’s dynamic behavior. Linear regression models were applied to horizontal and vertical intensity distributions to assess long-term beam stability. The resulting predictive trends revealed a systematic drift in beam centroid position, most notably along the vertical axis, and a gradual broadening of the horizontal FWHM. The modeling further showed that vertical intensity increased over time while horizontal intensity displayed a slight decline, reinforcing the presence of axis-specific fluctuations. These effects are attributed to minor optical misalignments or thermally induced variations in the beam path. By integrating deterministic analysis with data-driven forecasting, this methodology offers a robust framework for real-time beam quality evaluation. It enhances sensitivity to subtle distortions and supports the future development of automated, self-correcting laser systems. The results underscore the critical role of continuous, high-resolution monitoring in maintaining beam stability and alignment precision in femtosecond laser applications. Full article

Methylammonium chloride (MACl) in perovskite solar cells (PSCs) is a key additive known to enhance film quality in dimethyl sulfoxide (DMSO)-based systems, where an optimal concentration of 50 mol% is typically required. However, alternative solvent systems, such as N-methyl-2-pyrrolidone (NMP), have shown potential to reduce additive concentrations while maintaining high performance. This study explored the NMP/DMF (1:9) solvent system and its impact on MACl optimization. The optimal concentration of MACl in NMP-based systems was reduced to 20–30 mol%, representing a substantial decrease from the 50 mol% typically required in DMSO-based formulations. Films produced under these conditions exhibited superior crystallinity, as evidenced by narrower full-width at half maximum (FWHM) values in X-ray diffraction (XRD), and reduced defect densities. These structural improvements translated into enhanced optoelectronic properties, with devices achieving efficiency exceeding 23%, compared with ~20% for DMSO-based counterparts. Furthermore, the NMP-based system demonstrated improved long-term stability under continuous illumination. Full article

Two innovative dimeric derivatives of indolo[3,2,1-jk]carbazole (ICz), named 7,7′-biindolo[3,2,1-jk]carbazole (ICzDO) and 4,4′-biindolo[3,2,1-jk]carbazole (ICzDM), have been developed. Both dimers consist of two ICz units coupled through distinct ortho and meta positions. In the solution state, ICzDO and ICzDM exhibited photoluminescence (PL) maxima at 379 nm and 391 nm, demonstrating emission in the deep-blue region. These compounds show exceptionally narrow emission spectra, characterized by full width at half maximum (FWHM) of 28 nm for ICzDO and 26 nm for ICzDM. In the film state, ICzDM exhibited a photoluminescence (PL) maximum at 428 nm, whereas ICzDO showed a red-shifted emission at 507 nm with a broad full width at half maximum (FWHM) of 87 nm, indicating significant red-shifted excimer emission characteristics. This is attributed to its aggregation-enhanced excimer emission (AEEE) characteristics. When used as host materials for red phosphorescent OLEDs, both compounds enabled efficient energy transfer. Devices using ICzDM as the host attained highly efficient external quantum efficiency (EQE) values of 13.5%, coupled with remarkable color purity represented by Commission Internationale de l’Éclairage (CIE) coordinates of (0.685, 0.314). These findings emphasize how strategic variations in linking positions of identical chromophores can markedly enhance OLED device performance, paving the way for innovative material designs in next-generation organic semiconductor technologies. Full article

Integrated light-emitting diodes (LEDs) with waveguides play an important role in applications such as augmented reality (AR) displays, particularly regarding coupling efficiency optimization. Quantum dot light-emitting diodes (QLEDs), an emerging high-performance optoelectronic device, demonstrate substantial potential for next-generation display technologies. This study investigates the influence of microcavity modulation on the output of QLEDs coupled with a silicon nitride (SiNx) waveguide by simulating a white light QLED (W-QLED) with a broad spectrum and mixed RGB QDs (RGB-QLED) with a comparatively narrower spectrum. The microcavity converts both W-QLED and RGB-QLED emissions from broadband white-light emissions into narrowband single-wavelength outputs. Specifically, both of them have demonstrated wavelength tuning and full-width at half-maximum (FWHM) narrowing across the visible spectrum from 400 nm to 750 nm due to the microcavity modulation. The resulting RGB-QLED achieves a FWHM of 11.24 nm and reaches 110.76% of the National Television System Committee 1953 (NTSC 1953) standard color gamut, which is a 20.95% improvement over W-QLED. Meanwhile, due to the Purcell effect of the microcavity, the output efficiency of the QLED coupled with a SiNx waveguide is also significantly improved by optimizing the thickness of the Ag anode and introducing a tilted reflective mirror into the SiNx waveguide. Moreover, the optimal output efficiency of RGB-QLED with the tilted Ag mirror is 10.13%, representing a tenfold increase compared to the sample without the tilted Ag mirror. This design demonstrates an efficient and compact approach for the near-eye full-color display technology. Full article

This study presents a numerical investigation of surface plasmon resonance (SPR) sensors based on multilayer configurations incorporating BK7, silver, silicon nitride (Si₃N₄), and black phosphorus (BP). Using the transfer matrix method, the optical performance of four architectures was evaluated under refractive index perturbations consistent with values reported in prior theoretical and experimental studies. The sensor response was characterized through metrics such as angular sensitivity, resonance shift, full width at half maximum, attenuation, and derived figures including detection accuracy and limit of detection. Parametric optimization was performed for the thickness of each functional layer to enhance sensing performance. Among all configurations, those incorporating both Si₃N₄ and BP demonstrated the highest angular sensitivity, reaching up to 394.46°/RIU. These enhancements were accompanied by increased attenuation and spectral broadening, revealing trade-offs in sensor design. The results, based entirely on numerical modeling, provide a comparative framework for guiding SPR sensor optimization under idealized optical conditions. Full article

This research introduces a biosensor utilizing surface plasmon resonance in a photonic crystal fiber (PCF) configuration. PCF uses fused silica as the base material, with a layer of gold placed over the U-channels in the cross-section of the fiber to create a surface plasmon resonance. There are three different sizes of internal fiber optic air hole diameters, with a larger channel circle below the u-channel for the formation of an energy leakage window. COMSOL software 6.0 assisted us in tuning the fiber optic structure and performance for the study, and the structural parameters analyzed mainly include the channel circle diameter, the channel circle spacing, the profundity measurement of the polished layer, and the nanoscale size variation of metal films. The results of the simulation study show that the optical fiber sensor achieves refractive index (RI) responsiveness across the 1.30 to 1.41 range, and in the RI interval of 1.40 to 1.41, the sensor exhibits the largest resonance peak shift, and its highest sensitivity reaches 10,200 nm/RIU, and the smallest full width at half peak (FWHM) corresponds to the RI of 1.34 with a value of 4.8 nm, and the highest figure of merit (FOM) corresponds to the RI of 1.34 with a value of 895.83 (1/RIU). COMSOL 6.0 simulation software, was used to simulate the changes in blood refractive index corresponding to different glucose concentrations, and the detection performance of the sensor for different concentrations of glucose was tested. Then, the results show that the glucose concentration in 75 mg/dL–175 mg/dL with RI detection sensitivity is 3750 nm/RIU, where the maximum refractive index sensitivity is 5455 nm/RIU. It shows that the sensor can be applied in the field of biomedical applications, with its convenience, fast response, and high sensitivity, it has great potential and development prospect in the market. Full article

Researchers frequently utilize the method of optical initial structure (MOIS) of Czerny–Turner (C–T) spectrometers for aberration-correction studies based on the coma-free equation. While effective, this method has limitations: small numerical apertures at slits (0.05–0.07) hinder weak signal detection; V or W-shaped variations in Airy disk across wavelengths; optical resolution depends on the radius of the collimating lens may not match detector resolution; and sequence patterns based on the spot diagrams cannot simulate the full width at half maximum (FWHM) under discrete sampling. To address these issues, using ray tracing and imaging equations, three criteria are proposed: luminous flux and aberration balance (LFAB), Airy disk variation at imaging points (ADVI), and optical-detector resolution matching (ORDR). A verification system with a 500–750 nm wavelength range and 0.4 nm resolution was designed. Results show that designing spectrometers based on these criteria increases the slit’s numerical aperture to 0.11 while controlling aberrations. After optimization, the tangential Airy disk size decreased by 28% with variations within 3 μm. Discrete sampling indicates FWHM pixel errors remain within 1/2 pixel of the theoretical value, and FWHM is at least 2.5 pixels, satisfying stricter sampling requirements beyond Nyquist. Optimization only involves adjusting the image plane by 0.017 mm axially, 0.879 mm off-axis, and 0.48° eccentricity. This research strengthens spectrometer design theory and improves practical applications. Full article