Search Results (240)

A seven-layer broadband antireflection coating consisting of Al₂O₃, TiO₂, SiO₂, and MgF₂ was designed and deposited on both sides of K9 glass for the 400–1100 nm range. The deposition parameters for TiO₂ and SiO₂ single layers were optimized, and the measured optical constants were used in TFCalc to refine the multilayer design. Layer-specific thickness-tolerance analysis was performed to identify the layers requiring strict process control. The initially characterized double-sided coating showed an average transmittance of 98.72% over 400–1100 nm. Four samples prepared in one additional deposition batch exhibited closely matching transmittance spectra, indicating low sample-to-sample variation within that batch. Five-position profilometry indicated consistent total-thickness control. Cross-sectional scanning electron microscopy (SEM) revealed well-defined multilayer contrast without obvious cracking, and regional energy-dispersive X-ray spectroscopy (EDS) analysis detected the constituent elements of the coating. These results demonstrate a practical design-to-fabrication approach that combines process-specific optical constants with tolerance analysis, with potential applications in imaging systems, optical windows, and lidar. Full article

Despite recent advances in computer vision and optical imaging, the image-based recognition of ophthalmic lens categories characterized by different refractive indices and anti-reflective coating types remains largely unexplored. In this work, we formulate this problem as a non-destructive optical inspection task, where lens-induced visual changes are treated as subtle micro-texture signatures produced by the interaction between the lens and a controlled visual target. Although these signatures are often imperceptible to the human eye, they can be quantified using local texture analysis. To establish the first systematic benchmark for this emerging application, we present a comprehensive evaluation of state-of-the-art local texture descriptors, with particular emphasis on Local Binary Pattern (LBP)-like methods, under unified evaluation protocols. The evaluation is conducted on two dedicated ophthalmic lens image datasets acquired under controlled conditions, using consistent visual targets designed to reveal lens-induced texture and color variations. This setting enables a rigorous assessment of whether handcrafted micro-texture descriptors can capture discriminative image signatures associated with different refractive indices and anti-reflective coating types. The experimental results demonstrate that several modern LBP variants provide excellent recognition performance, confirming the relevance of local micro-texture analysis for image-based ophthalmic lens category recognition. Comparisons with pretrained deep feature extractors further show that although deep representations generally achieve the highest recognition rates, several handcrafted descriptors offer comparable performance while requiring neither network training nor fine-tuning. Beyond recognition accuracy, the benchmark investigates performance stability across datasets, robustness under limited training samples, classifier influence, and the statistical significance of the observed performance differences. Overall, this work establishes the first reproducible image-based benchmark for non-destructive ophthalmic lens inspection and provides practical guidelines for selecting local texture descriptors in ophthalmic lens recognition systems. Full article

We demonstrate a novel method for fabricating densely packed, high-aspect-ratio cavities (depth to diameter ratio > 1) in silicon wafers coated with diamond-like carbon (DLC). The process combines femtosecond laser irradiation with subsequent wet etch (potassium hydroxide-based) or plasma etch (chlorine- and oxygen-based). The femtosecond laser is used to pattern precise openings in the DLC layer, exposing the underlying silicon, which is then rapidly etched to form well-defined cavities. This combined laser ablation and etching approach enables high-throughput fabrication of densely packed micrometer cavities and offers scalability toward industrial production. The resulting hybrid DLC-coated silicon structure, featuring densely packed cavities, may exhibit antireflective properties in the far-infrared spectrum range. Full article

In the present paper, we studied the interaction of microwave radiation with conductive indium tin oxide (ITO) coatings deposited on a borosilicate glass. The experiments were carried out with the ITO films, the thickness of which varied in the range from 85 to 607 nm. The transmittance and reflectivity of the ITO film/K108 glass structures were measured in the frequency region from 3 to 23 GHz. Theoretical modeling of the spectra was performed by means of the transfer matrix method. It was shown that for a given thickness of the glass substrate, the transmission and reflection spectra of the ITO film/K108 glass structures were fully determined by only one parameter of the ITO film, namely, its DC sheet resistivity. The considered model predicts an increase in maximum microwave shielding effectiveness up to 45.6 dB with a decrease in DC sheet resistivity to 1 Ohm/sq. ITO coatings with DC sheet resistivities down to 2.3 Ohm/sq have been experimentally investigated. The model microwave transmittance and reflectivity spectra were in good agreement with the experimental ones. In particular, the coefficient of determination for the transmittance spectra was rather high: R² > 0.93. It was experimentally demonstrated that applying antireflective coatings on both sides of the ITO film/K108 glass microwave shielding filter significantly improved its transparency in the operating optical range. A filter has been created that provides microwave shielding effectiveness of 38.7 dB with an average transmission coefficient of 0.81 in the visible range. Full article

The evolution of 193 nm deep-ultraviolet (DUV) lithography toward high numerical aperture (NA > 1.35) presents challenges approaching physical limits for antireflective (AR) coatings on strongly curved lens elements. In this study, a full-stack multi-objective optimization framework is developed by coupling the Non-dominated Sorting Genetic Algorithm II (NSGA-II) with the Transfer Matrix Method (TMM) to optimize a 7-layer LaF₃/MgF₂ system on strongly curved substrates ($R=150$ mm). The model integrates material dispersion, thermo-optic effects, deposition flux deviations, and manufacturing thickness constraints. Following 1500 generations of optimization and TOPSIS-based decision-making, the selected Pareto optimal solution achieves a full-aperture average reflectance of 1.3633% and a radial uniformity of 9.5037%. The design further exhibits high environmental robustness with a thermal drift of 0.0019% and a residual stress of 39.23 MPa. These results demonstrate that the proposed method overcomes the critical process bottleneck of achieving full-aperture uniformity below 10% on strongly curved optics. This framework provides a general paradigm for the robust design of next-generation ultra-precision DUV optical systems, effectively balancing theoretical depth with engineering feasibility. Full article

Photovoltaic modules require efficient sunlight modulation, including enhanced visible transmittance and conversion of unused ultraviolet light. This study develops a synthetic optical coating that achieves both functions by integrating down-conversion BAM (BaMgAl₁₀O₁₇:Eu²⁺, Mn²⁺) nanophosphors into a silica anti-reflection sol. The key novelty lies in a synergistic surface engineering strategy that decouples dispersion stabilization from luminescence protection. Five dispersants are systematically compared under combined ball and sand milling. The polyester-modified acrylic long-chain dispersant (DK062) yields a stable nanodispersion with an average particle size of 228 nm and a Zeta potential of −7.61 mV, effectively suppressing re-agglomeration while retaining high photoluminescence. Subsequent surface modification with KH570 grafts a dense silane passivation layer via Si–O–M covalent bonds, further increasing the photoluminescence intensity by 1.39-fold. The optimized nanophosphors are incorporated into a commercial anti-reflection sol and dip-coated onto photovoltaic glass. At a doping concentration of 2‰ and a withdrawal speed of 8 mm/s, the resulting DCSAR coating exhibits an average transmittance of 91.16%—slightly higher than that of the pure anti-reflection coating (90.96%)—while showing strong green emission at 515 nm. Industrial on-site testing further demonstrates an average transmittance of 94.20%–94.31% with uniform green emission. This work provides a scalable route to fabricate highly transparent, light-converting anti-reflection coatings by combining dispersant-assisted milling and silane passivation. Full article

Laser-induced damage of sol–gel SiO₂ antireflection coatings remains a key reliability issue in high-power laser systems because porous networks, residual hydroxyl groups, and defect-related absorption centers can trigger localized heating and stress concentration under nanosecond irradiation. In this work, continuous-wave CO₂ laser conditioning was used as a localized post-treatment method to regulate the microstructure of sol–gel SiO₂ coatings on fused silica substrates. The revised manuscript clarifies the processing window, scanning parameters, laser damage testing protocol, and the sample-specific nature of the reported LIDT values. Laser conditioning induces partial densification of the porous coating, dehydration of Si-OH groups, relaxation of the Si-O-Si network, and enhancement of mechanical properties. Under the optimized conditioning condition, the surface roughness decreases from 14.08 nm to 9.76 nm, and the LIDT at 1064 nm increases from 4.8 J/cm² to 7.0 J/cm². The LIDT values are discussed as a relative microstructure–property comparison for the present coating system rather than as the upper technological limit of sol–gel silica coatings. Combined FTIR analysis, thermal simulation, morphology observation, and damage probability analysis indicate that the improvement originates from the combined effects of reduced defect absorption, moderated porosity, improved heat dissipation, and enhanced resistance to thermally induced cracking. The results provide a mechanism-guided strategy for using CO₂ laser conditioning to tune sol–gel silica coatings while also identifying the need for further validation on higher-LIDT coatings and at application-relevant wavelengths. Full article

Chalcopyrite-based thin-film solar cells have great potential for various applications, such as top or bottom cells in tandem devices, in addition to their use as standard single-junction modules due to their tuneable bandgap energy. A bandgap energy E_g > 1.5 eV should be targeted to realize a wide-bandgap top cell, e.g., by increasing the [Ga]/([Ga] + [In]) (GGI) ratio in Cu(In,Ga)Se₂ (CIGS) cells to the range of 0.7–1. A second approach is targeting the second theoretical efficiency maximum at a little lower E_g = 1.34 eV with a GGI around 0.6 for high-efficiency single-junction applications with reduced electrical losses. An industry-relevant (Ag,Cu)(In,Ga)Se₂ (ACIGS) co-evaporation process for wide-bandgap cells fabricated with GGI ratios above 0.6, with moderate [Ag]/([Ag] + [Cu]) (AAC) ratios < 0.1 and in-line RbF-PDT, was established on molybdenum-coated soda-lime glass substrates. Both measures, Ag alloying and RbF-PDT, can increase power conversion efficiency (PCE) mainly due to improved open-circuit voltage (V_OC). In addition, Ag addition can increase fill factor (FF)_, leading to an increase in the PCE for cells with GGI > 0.6 compared to Ag-free reference cells. (Zn,Mg)O, either with a [Mg]/([Mg] + [Zn]) ratio of 0.15 or 0.25, is a good option as high-resistive layer replacing the commonly used i-ZnO in combination with a CdS buffer. Our best ACIGS wide-bandgap solar cells with RbF-PDT and Zn_0.85Mg_0.15O (without anti-reflective coating (ARC)) from various experimental campaigns show a PCE of 12.7% (E_g = 1.50 eV), and with a slightly reduced E_g of 1.45 eV a PCE of 15.5%, with V_OC of 933 mV (V_OC deficit of 517 mV), and a good FF of 73.2%. In the case when the bandgap is significantly lowered to 1.34 eV (GGI = 0.61), to the second theoretical efficiency maximum, we achieved a PCE of 18.2% with ARC for an Ag-free CIGS cell with RbF-PDT. For this cell with a CdS/i-ZnO buffer system the V_OC deficit is 480 mV, and the FF is 78.1%. Full article

In this study, a non-typical luminescent organosilicone was synthesized through a click reaction and used as a cross-linker to cure hydroxyl-terminated dimethylsilicone oil at room temperature via the sol–gel process, followed by application as a coating on a glass surface. This organosilicone film functions effectively as a luminescent down-shifting (LDS) material. Additionally, the presence of methyl groups and voids in the structure imparts a low refractive index, allowing it to serve as an anti-reflective (AR) layer. Optical and structural analyses on organosilicone-coated glass samples were conducted, and the dual-functional layer was applied to the glass cover of a perovskite solar panel to evaluate its performance. The coating not only enhanced light transmission as an AR layer but also converted UV light into blue light, which was absorbed by the solar cell. The results indicated improved solar panel performance, particularly in short-circuit current (Isc), external quantum efficiency (EQE) in the UV wavelength range, and overall efficiency. Overall, this material is a promising candidate for solar panel applications owing to maximized UV absorption for LDS, preserved transparency of the top cover glass, and room-temperature gelation, which facilitates repair of the dual-functional coating. Full article

A compact, low-cost star tracker system tailored for small satellite applications was designed and prototyped. The system was designed with a fast f/1.2 aperture, a 20 × 13° field of view, and a theoretical angular resolution of 10 arcs—sufficient for the determination of attitude and orbit of a satellite. The optical design is based on a monolithic Maksutov–Cassegrain architecture, with lens assemblies fabricated from CR39 or PMMA to eliminate collimation requirements and improve vibration resistance. The lens was machined using Single-Point Diamond Turning to a precision better than λ/14. It was coated with a multilayer antireflective and highly reflective coatings applied via magnetron sputtering to reduce stray reflections and improve light throughput. The housing was produced using electron beam powder-bed fusion with Ti-64 alloy, while the use of commercial imaging sensors minimizes overall cost. Prototype testing confirmed to plate-solve star patterns with precision better than 27 arcs at 100 ms imaging time across all analysed images. Full article

The suppression of residual reflectivity in optical elements has become a hot research topic as it addresses the degradation of optical system imaging quality caused by stray light. Antireflective coatings on the outer surface of window glasses require low reflectivity, high hardness, and resistance to mechanical wear. This study investigates the role of reactive gas stoichiometry in tailoring the structure and performance of ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ antireflection (AR) coatings deposited on GG7i glass via capacitively coupled radio-frequency magnetron sputtering. First, the influence of three ${\mathrm{N}}_2$/${\mathrm{O}}_2$ flow ratios on the optical and mechanical properties of ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films discussed under identical process parameters. Results show that the refractive index, hardness, and surface roughness of the ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films increase with increasing ${\mathrm{N}}_2$/${\mathrm{O}}_2$ ratio and that the stress of the ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films increases according to the Stoney formula. The wear resistance of the ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films combined with an antifingerprint (AF) coating is tested using steel wool. Experimental results show that the water contact angle of the AF decreases with increasing surface roughness of the film. Finally, on the basis of a comprehensive evaluation of optical and mechanical properties, the antireflection coating on the outer surface of the window glass was prepared by optimizing the process parameters. At $0^{°}$ incidence, the average reflectivity from 420 to 680 nm is <1%, the maximum value is <1.2%, the surface hardness is 17.2 GPa, and the water contact angle is ${100}^{°}$ after the steel wool wear test, showing its suitability for durable antifingerprint applications. This work provides a strategic pathway for designing high-performance optical coatings with tailored mechanical robustness. Full article

Interdigitated back-contact solar cells were fabricated entirely with inkjet printing. poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), TiO₂, and metal lines were printed on a textured silicon substrate with only one inkjet printer. No vacuum deposition or diffusion of a back surface field is needed for the printed IBC solar cell. Adding co-solvent to the PEDOT:PSS and passivation of the Si surface significantly reduced the losses and enhanced the short-circuit current, Jsc, and, as a result, improved the fill factor and efficiency of the devices. The thickness of the PEDOT:PSS layer is approximately half a micrometer measured by profilometer, which is thicker than the optimal range typically reported; there is still a best short-circuit current, Jsc, of 19.2 mA/cm². To further improve the performance of the devices, an anti-reflective coating on the front side is required. Also, an improved metal contact ink is needed to improve the contact resistance between the PEDOT:PSS layer and the metal contact. The initial performance of all printed cells are compared to conventionally fabricated devices. Full article

The design of broadband, high-efficiency solar absorbers remains challenging due to the complex and ill-posed inverse mapping from the target optical responses to the physical structures in inverse design optimization. To address this, we propose a joint forward–inverse deep learning framework that enables the rapid and accurate optimization of multilayer metamaterial absorbers. This method integrates an inverse network based on a Modified Swin Transformer with a Multilayer Perceptron forward proxy and performs end-to-end training in a consistency-driven cycle. This strategy reduces the one-to-many ambiguity in inverse design and improves the prediction accuracy, with normalized test mean squared errors of 7.2 × 10⁻⁵ (inverse) and 6.8 × 10⁻⁵ (forward). Using this framework, we optimized an absorber comprising W/SiO₂ hyperbolic metamaterial stacks and TiO₂/SiO₂ anti-reflection coatings, achieving 97.4% average absorptivity across the 400–1750 nm solar spectrum, along with polarization insensitivity and robust wide-angle performance up to 60° incidence. The outdoor solar heating tests showed that the fabricated absorber reaches a peak temperature of 86.3 °C under natural sunlight, with an irradiance peak of about 850 W/m² at noon. This work shows that combining forward and reverse deep learning provides a powerful and scalable paradigm for accelerating the intelligent design of high-performance solar thermal metamaterials. Full article

In high-precision optical systems such as laser optics, astronomical observation, and semiconductor lithography, anti-reflection coatings are crucial for light transmittance, imaging quality, and stability, but traditional designs face modeling challenges in balancing ultralow reflectivity, high wavefront quality, and manufacturability amid multi-dimensional parameter coupling and multi-objective constraints. This study addresses these by proposing a unified mathematical modeling framework integrating a Symmetric five-layer high-low refractive index alternating structure (V-H-V-H-V) with dual-scale nanostructures, employing a constrained quasi-Newton optimization algorithm (L-BFGS-B) to minimize reflectivity, wavefront root-mean-square (RMS) error, and surface roughness root-mean-square (RMS) in a six-dimensional parameter space. The Sellmeier equation is adopted to calculate wavelength-dependent material refractive indices, the model uses the transfer matrix method for the Symmetric five-layer high-low refractive index alternating structure’s reflectivity, incorporates nano-surface height function gradient correction, sub-wavelength modulation, and radial optimization, applies Zernike polynomials for low-order aberration correction, quantifies surface roughness via curvature proxies, and optimizes via a weighted objective function prioritizing low reflectivity. Numerical results show the spatial average reflectivity at 632.8 nm reduced to 0.13%, the weighted average reflectivity across five representative wavelengths in the 550–720 nm range to 0.037%, the reflectivity uniformity to 10.7%, the post-correction wavefront RMS to 11.6 milliwavelengths, and the surface height standard deviation to 7.7 nm. This framework enhances design accuracy and efficiency, suits UV nanoimprinting and electron beam evaporation, and offers significant value for high-power lasers, lithography, and space-borne radars. Full article

Silicon windows in wafer-level packaged LWIR sensors suffer ~30% Fresnel reflection per interface, limiting optical throughput and detector sensitivity. We present an end-to-end design, fabrication, and validation framework for CMOS-compatible moth-eye anti-reflection coatings patterned directly on silicon wafers. Our approach integrates the effective medium theory, a transfer matrix analysis, full-wave FDTD simulations, and experimental Fourier-transform infrared (FTIR) measurements to optimize subwavelength pillar arrays for broadband (8–14 μm) and angle-tolerant performance. Fabricated structures demonstrate a 46.7% responsivity boost in CMOS–SOI–MEMS thermal sensors compared to bare silicon windows, while simulations predict up to 85.1% transmission and 57.1% responsivity enhancement for double-sided patterning. These results establish moth-eye metasurfaces as a scalable, CMOS-compatible solution for next-generation wafer-level processing and packaging infrared sensing platforms, transforming optical improvements into measurable electrical performance gains. The contribution of this work is the end-to-end framework for designing moth-eye wafer level processing and packaging for “real-life” CMOS-compatible infrared sensors manufacturing. Full article