Search Results (212)

An external power build-up cavity of a line-narrowed 407-nm laser diode for Raman gas analysis was demonstrated to possess good gas detection capabilities. By employing an ordinary laser diode without anti-reflection coating or and a bandpass interference filter in an external cavity resonance, the laser linewidth was narrowed by resonant optical feedback, and tens of watts of external cavity power were built up. The coupling mechanism between the semiconductor laser and the external cavity are discussed, as well as the noise background in the experimental results. The Raman spectrum of ambient air was analyzed, achieving a methane detection limit of 1 ppm. Full article

Scattered light makes up a significant amount of recorded intensities during tomographic imaging, thereby leading to severe misinterpretation and artifacts in the reconstructed volume images. Correcting artificial intensities that stem from scattered light, therefore, is of primary interest and demands quantitative measurements. While numerous methods have been developed to reduce X-ray scattering artifacts, fewer methods deal with optical scattering. In this study, a measurement method for determining optical scattering in scintillators is presented with the aim of further developing correction algorithms. A theoretical model based on internal multiple reflections was developed for this purpose. This model assumes an additive exponential kernel with a certain scattering length to the system’s point spread function. This assumption was confirmed, and the scatter length was estimated from three new different kinds of experiments (hgap, rect, and LSF) on the BM18 beamline of the European synchrotron. The experiments further revealed significant differences in scattering proportion and length when different coatings are applied to the front and back faces of crystalline LuAG scintillators. Anti-reflective coatings on the backside show an effect of reducing the scattering magnitude while reflective coatings on the front side increase the proportion of the unscattered signal and, thus, show proportionally less scattering than black coating or no front coating. In particular, roughened black coating is found to worsen optical scattering. In summary, our results indicate that a combination of reflective (front) and anti-reflective (back) coatings yields the least optical scattering and, hence, the best image quality. Full article

The scope of this study was to evaluate the response of Ce-doped gadolinium aluminum gallium garnet (GAGG:Ce) crystalline scintillator under medical X-ray irradiation for medical imaging applications. A 10 × 10 × 10 mm³ crystal was irradiated at X-ray tube voltages ranging from 50 kVp to 150 kVp. The crystal’s compatibility with several commercially available optical photon detectors was evaluated using the spectral matching factor (SMF) along with the absolute efficiency (AE) and the effective efficiency (EE). In addition, the energy-absorption efficiency (EAE), the quantum-detection efficiency (QDE) as well as the zero-frequency detective quantum detection efficiency DQE(0) were determined. The crystal demonstrated satisfactory AE values as high as 26.3 E.U. (where 1 E.U. = 1 μW∙m⁻²/(mR∙s⁻¹)) at 150 kVp, similar, or in some cases, even superior to other cerium-doped scintillator materials. It also exhibits adequate DQE(0) performance ranging from 0.99 to 0.95 across all the examined X-ray tube voltages. Moreover, it showed high spectral compatibility with commonly used photoreceptors in modern day such as complementary metal–oxide–semiconductors (CMOS) and charge-coupled-devices (CCD) with SMF values of 0.95 for CCD with broadband anti-reflection coating and 0.99 for hybrid CMOS blue. The aforementioned properties of this scintillator material were indicative of its superior efficiency in the examined medical energy range, compared to other commonly used scintillators. Full article

We present a practical numerical model for calculating transmittance and reflectance of multilayer antireflection coatings taking third-order optical nonlinearities into account. Thereby, the impact of different types of discretization of the complex refractive index profile on the predicted system performance is investigated. Additionally, aspects of parallelism of the calculations are discussed. It is shown that the inclusion of nonlinearity is essential when large laser intensities are incident to the coating. The developed method is applied for the design of different antireflective coatings matching various types of targets. Full article

This study aims to develop a stress-optimized ultra-broadband beam-splitting coating that integrates four spectral bands by analyzing the beam-splitting properties of coatings spanning visible to medium and long-wave infrared regions. A beam-splitting coating was deposited on a Ge substrate using ion-beam-assisted thermal evaporation, employing Ge, ZnS, and YbF₃ as coating materials. The designed coating exhibits high reflectance in the 0.5–0.8 μm and 0.9–1.7 μm wavelength bands while maintaining high transmittance in the 3–5 μm and 8–12 μm bands. The optimal deposition process for a single-layer coating was established, at a 45° incidence angle, the beam-splitting coating achieved an average reflectance (Rave) of 86.6% in the 0.9–1.7 μm band and 93.7% in the 0.9–1.7 μm band, alongside an average transmittance (Tave) of 91.36% in the 3–5 μm band and 91.3% in the 8–12 μm band. The antireflection coating achieved a single-side Tave of 98.5% in the 3–5 μm band and 97% in the 8–12 μm band. The coating uniformity exceeded 99.6%. To optimize the surface profile, a single-layer Ge coating was added to the rear surface, resulting in a root mean square deviation of less than 0.0007 μm, achieved the same precision of the surface profile successfully. The deposited beam-splitting coating possessed high surface profile precision, and successfully achieved high reflectance in the visible to short-wave infrared range and high transmittance in the medium- and long-wave infrared range. The coating demonstrated excellent adhesion, abrasion resistance, and structural integrity, with no wrinkling, cracking, or delamination. Full article

Long-term stability and laser-induced damage resistance of optical components in the UV region are critical for enhancing their performance in UV high-power laser applications. This study evaluates the laser-induced damage threshold (LIDT) of commercially available UV optical windows with anti-reflective (AR) coating, produced through various coating techniques and designed for high-power lasers. A third-harmonic (343 nm) wavelength with good beam quality was generated in the picosecond regime to investigate the LIDT of optical components. The LIDT for each sample was measured under controlled conditions and compared based on their coating techniques. The sample coated with Al₂O₃/SiO₂ through ion beam sputtering has the best LIDT value, of 0.6 J/cm², among the tested samples, based on the hundred-thousand-pulses methodology. The damage threshold curve and the corresponding damage morphology are discussed in detail, and these findings provide insights into the durability and susceptibility of UV optics for advanced laser systems available in the market. Full article

Recent advancements in photonics have intensified the performance requirements for optical systems and present significant challenges for optical coating technologies. Conventional interference coating systems often prove to be insufficient, especially in applications requiring large angles of light incidence or a wide wavelength range. Nanostructures, which consist of an air material mixture, offer promising alternatives. In this work, silica nanostructures are manufactured by the AR-plas2 method, in which first an organic layer is evaporated onto a substrate. This organic layer forms self-organizing nanostructures by a plasma etching step, which are subsequently coated with silica. Finally, the organic residues are removed by additional plasma etching and heat treatment steps, which results in hollow silica structures. The work examines the optical and functional properties of these structures designed for 355 nm to demonstrate their use as anti-reflective coatings for advanced optical systems. Full article

In this study, ZnS/YbF₃-10.6 µm antireflection (AR) coatings were fabricated on CVD single-crystal diamond and ZnSe substrates. The spectral characteristics of the coatings and their performance under continuous wave laser radiation at 10.6 µm were systematically investigated. The fabricated AR coatings exhibited excellent spectral properties in the target wavelength range. Both theoretical calculations and experimental results indicated that, at the same power density, the 10.6 µm AR coatings on diamond substrates exhibited a lower temperature rise compared to those deposited on ZnSe substrates. Due to its high thermal conductivity, the diamond substrate is expected to exhibit reduced thermally induced surface distortion. The laser-induced damage threshold (LIDT) test results indicate that the AR coating deposited on the ZnSe substrate exhibits a damage threshold of 11,890 W/cm², whereas the AR coating on the diamond substrate achieves a threshold of 15,287 W/cm², representing a 28.5% improvement over the ZnSe substrate. Additionally, graphite formation occurs on the diamond substrate under high power density. These findings provide both theoretical and experimental support for the potential application of diamond materials in high-power laser systems. Full article

Modern multi-junction solar cell technology offers a pathway to achieving consistent and high photovoltaic conversion efficiencies through enhanced solar spectrum absorption. Indeed, during the last years, the industries of solar cells have focused on optimizing device structures, utilizing both robust and delicate materials to maximize their performances. This paper presents the modeling and optimization of the electrical and structural properties of high-efficiency InGaP/GaAs double-junction solar cells, specifically without employing an anti-reflective coating. This developed structure has been achieved by introducing a buffer layer in the lower layer and incorporating an upper back surface field layer into the investigated cell structure. Furthermore, the optimization conducted in this paper using Silvaco-Atlas software (version 2018) under the AM1.5G spectrum reveals that the proposed InGaP/GaAs tandem cell configuration exhibits significant performance, reaching conversion efficiency of 41.585%. It can be said that this adapted structure yields a short-circuit current density of 21.65 mA/cm², an open-circuit voltage of 2.319 V, and a filling factor of 84.001%. Whereas this newly optimized structure demonstrates its effectiveness in enhancing solar cell efficiency performance, presenting highly promising results with potential significance for the devices’ optical and electrical properties. Full article

Fog-proof coatings have been widely utilized in various fields, including automobile windshields, curtain walls, and fog-resistant eyewear. To date, numerous methods have been developed for preparing fog-proof coatings. However, the most effective fog-proof surfaces often suffer from poor light transmittance. In this report, we present a method for preparing fog-proof nano-coatings using atmospheric plasma spraying (APS). Hexamethyldisiloxane (HMDSO) was employed as a precursor solution, resulting in the formation of amorphous nano-coatings on glass substrates with a thickness ranging from 15 to 25 nm. The APS-coated glasses exhibit superhydrophilic properties, excellent fog resistance, and anti-reflective characteristics. Additionally, the APS coatings enhance light transmittance from 90% to 92%. Full article

This study investigates the potential of patterned multiple-layer anti-reflection coatings (MLARCs) integrated with nanocrystalline quantum dots (NQDs) to enhance silicon solar cell (Si-SC) performance by significantly reducing reflection losses. Through a combination of experimental characterization and numerical modeling, the impact of single-layer (SLARCs), continuous MLARCs, and patterned MLARCs on optical and electrical properties was assessed. The results demonstrate substantial improvements in light trapping and absorption through the implementation of patterned MLARCs. Full article

Nanopatterning of signal-transmitting proteins is essential for cell physiology and drug delivery but faces challenges such as high cost, limited pattern variability, and non-biofriendly materials. Arthropods, particularly beetles (Coleoptera), offer a natural model for biomimetic nanopatterning due to their diverse corneal nanostructures. Using atomic force microscopy (AFM), we analyzed Coleoptera corneal nanocoatings and identified dimpled nanostructures that can transform into maze-like/nipple-like protrusions. Further analysis suggested that these modifications result from a temporary, self-assembled process influenced by surface adhesion. We identified cuticular protein 7 (CP7) as a key component of dimpled nanocoatings. Biophysical analysis revealed CP7’s unique self-assembly properties, allowing us to replicate its nanopatterning ability in vitro. Our findings demonstrate CP7’s potential for bioinspired nanocoatings and provide insights into the evolutionary mechanisms of nanostructure formation. This research paves the way for cost-effective, biomimetic nanopatterning strategies with applications in nanotechnology and biomedicine. Full article

In this work, we demonstrate an advanced light management strategy for bifacial perovskite solar cells incorporating a silica-based anti-dust and anti-reflection (AR) coating. The silica layer provides dual functionality, enhancing optical efficiency through effective reflection suppression and protecting the solar cell surface from environmental contaminants, especially dust. The hydrophobic nature of the silica coating further prevents accumulation of dust and particulate matter, supporting a self-cleaning mechanism that maintains cell transparency and performance over extended periods. The simulation results indicated that transitioning from a monofacial to a bifacial design with a silica layer on top had a considerable impact on the PSC performance. The optimized bifacial structure demonstrated high-performance metrics, achieving a voltage of 1.35 V, a fill factor of 84.24%, a current density (J_SC) of 29.10 mA/cm², and a power conversion efficiency of 31.00% when illuminated from the electron transport layer side. When illuminated from the hole transport layer side, the structure attained an efficiency of 22.00% with a calculated bifaciality factor (BF) of 72.12%, highlighting the potential of bifacial PSC design. Our findings reveal that the addition of the silica layer led to a notable improvement in light harvesting efficiency. Full article

Renewable energy is in high demand, with significant contributions from the solar industry encouraging research into more efficient, cost-effective, and versatile solar cell technologies. Anti-reflection coating (ARC) is an important method for improving solar cell efficiency by minimizing light reflectance and maximizing photon absorption. This study investigates the electrical and optical behaviors of single- and double-layer ARCs for gallium arsenide (GaAs) solar cells, using PC1D simulation for single-layer SiO₂, and ZnSe, and double-layer SiO₂/ZnSe configurations. The findings indicate that the double-layer SiO₂/ZnSe ARC structure significantly reduces reflectance and enhances light absorption, leading to a higher current density (J_sc) and overall efficiency. With optimized layer thicknesses of 60 nm (ZnSe) and 100 nm (SiO₂), the efficiency increased from 20.628% to 30.904%, representing a 49.81% improvement. This enhancement is primarily attributed to the increased photon absorption and a higher electron–hole generation rate, confirming the superior performance of double-layer ARCs over single-layer configurations. Full article

External cavity quantum cascade lasers (EC-QCLs) utilizing the Littrow configuration and operating at an approximate wavelength of 8.5 μm have been successfully demonstrated in continuous wave operations at room temperature. Our work provides ideas and experimental support for the optimization of the EC-QCL which indicate optimal EC-QCL performance with an external cavity length of 25 cm and investigates the impact of various parameters, including injection current and temperature on the performance of the EC-QCL. In the absence of anti-reflection (AR) coating, the tuning range at 25 °C extends up to 103.3 cm⁻¹, while the maximum side mode suppression ratio (SMSR) reaches 30.8 dB, accompanied by a full width half maximum linewidth (FWHM) of 0.76 nm. Full article