Publication database
The industrial advancement of high-efficiency silicon solar cells increasingly depends on precise laser patterning and reliable silver-free metallization. For tunnel oxide passivated contact (TOPCon) devices, laser contact opening on the rear side faces a critical trade-off: achieving sufficient surface roughening for robust electroplated adhesion while minimizing thermal damage to the sensitive passivating stack. Here, we demonstrate a transformative ultraviolet femtosecond laser strategy that effectively decouples these conflicting requirements for damage-free rear-side metallization. Atomic-resolution transmission electron microscopy systematically reveals the single-pulse ablation behavior, identifying an effective SiNx removal threshold of 0.105 J/cm2 and a passivating contact damage threshold above 0.17 J/cm2, thus defining a viable processing window for selective dielectric opening with preserved electrical integrity. Building on this, we introduce a novel twin-pulse irradiation approach that exploits nonlinear energy accumulation to generate functional laser-induced periodic surface structures (LIPSS) for potential enhanced mechanical anchoring, while highly confining substrate damage to a depth of ∼30 nm. This enables ultra-narrow grid fingers (7.1 μm) and exceptionally low specific contact resistivity (0.35 mΩ cm2) in Ni electroplated contacts. These results highlight ultraviolet femtosecond lasers as a scalable, high-precision tool for next-generation silver-free TOPCon metallization, paving the way for cost-effective mass production and further efficiency gains in silicon photovoltaics.
Laser-induced graphene (LIG) enables rapid conversion of polymer substrates into conductive carbon materials. In this study, nitrogen-containing carbon nanomaterials were fabricated on polyetherimide (PEI) substrates using empirical screening of two specific process points. The resulting materials were characterized using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy to correlate structural features with electron-transfer behavior. Raman and XPS analyses showed different structure and morphology depending on irradiation regime. The carbon materials with a higher sp3 fraction (≈55–59%), larger in-plane crystallite size (La up to 8.0 nm), and pronounced π–π* shake-up satellites indicated enhanced graphitic ordering when a shorter nanosecond laser was used. These structural differences resulted in substantially lower charge-transfer resistance (0.53–0.79 kΩ·cm3) and larger electroactive surface areas for the porous electrodes compared with foam structured carbon nanomaterials. The results show that, under the selected fabrication conditions, variations in laser processing parameters correspond to differences in graphitic ordering and electron-transfer properties in PEI-derived laser-induced carbon materials.
Direct-writing submicron copper circuits on glass with laser precision – without lithography, vacuum deposition, or etching – represents a transformative step in next-generation microfabrication. We present a high-resolution, maskless method for metallizing glass using ultrashort pulse Bessel beam laser processing, followed by silver ion activation and electroless copper plating. The laser-modified glass surface hosts nanoscale chemical defects that promote the in situ reduction of Ag+ to metallic Ag0 upon exposure to AgNO3 solution. These silver seeds act as robust catalytic and adhesion sites for subsequent copper growth. Using this approach, we demonstrate circuit traces as narrow as 0.7 µm, featuring excellent uniformity and adhesion. Compared to conventional redistribution-layer (RDL) and under-bump-metallization (UBM) techniques, this process eliminates multiple lithographic and vacuum-based steps, significantly reducing process complexity and production time. The method is scalable and adaptable for applications in transparent electronics, fan-out packaging, and high-density interconnects.
Teflon, or polytetrafluoroethylene (PTFE), is popular for high-frequency applications due to its low dielectric constant and high chemical resistance, but these properties also make it difficult to metallize for electronic uses because its inertness impedes metal adhesion and deposition. We present the design, simulation, and measurement of Sierpinski antenna for radio frequency energy harvesting, manufactured using the Selective Surface Activation by Laser (SSAIL) technique on flexible Teflon sheet. The results demonstrate that SSAIL is an excellent method for fabricating antennas on flexible surfaces, offering high performance and reliability. Electromagnetic simulations and experimental validations confirm the effectiveness of this approach for next-generation flexible communication devices and electronics.
The increasing demand for miniaturized and high-performance consumer electronics has driven advancements in packaging solutions, including the transition to glass interposers. One of the critical aspects of the development is the fabrication of high-density through-glass vias (TGVs). This article presents the formation of TGVs in various glass substrates using an industrial femtosecond laser FemtoLux 30 operating in different operation modes – single-pulse, MHz burst, GHz burst and MHz+GHz burst modes. By employing burst mode and advanced machining methods such as bottom-up milling – TGVs fabrication is possible. With specific parameter sets TGVs with aspect ratios exceeding 1:80 was achieved, with drilling times as low as 350 ms. Additionally, to address current challenges in making electric traces on substrates, it introduces Selective Surface Activation Induced by Laser (SSAIL) as a unique complementary metallization technology, enabling direct copper deposition on different materials like ceramic, plastics and most importantly – glass, for complete packaging workflows. The findings demonstrate the potential of the FemtoLux femtosecond laser as a high-throughput and precise solution not only for TGV fabrication, but also for Selective Surface Activation Induced by Laser (SSAIL) based metallization - supporting next-generation semiconductor advanced packaging solutions.
In today’s electronic applications, creating accurate conductive traces on flexible transparent polymers or glass for improved functionality is crucial. These microtraces serve as integral components for transparent electrodes, heating films, and arrays of responsive sensors. Microscale circuit interposers fabricated on glass substrates are essential to advanced electronics packaging and integration. Micro and submicron scale traces fabricated straight on glass can make breakthroughs in packaging technologies. In this study, we demonstrate the capabilities of Selective Surface Activation Induced by Laser (SSAIL) technology for forming micron traces on transparent materials: glass and polyethylene terephthalate film. Trace width dependency on laser processing parameters: pulse duration, pulse pitch, pulse repetition rate, laser fluence and beam polarization are investigated. Ultrashort laser beam focused with microscopic objective is used for surface activation for selective copper electroless plating. The width of trace formed on glass can be 1.5 µm and simultaneously demonstrate supreme adhesion to the substrate.
Intra-volume glass scribing for cutting is one of the most advanced applications of nondiffractive laser beams. However, ever-growing requirements from the industry for complexity, miniaturization, and quality of fabricated parts have pushed the technology forward. Most of the methods developed to improve glass scribing rely on spatial and temporal pulsed beam shaping. As another degree of freedom to manipulate light, polarization has received little attention so far. In this work, we investigate the effect of linear and circular polarizations on the volumetric modification and scribing of soda-lime glass using a zero-order Bessel beam in the MHz burst regime. We demonstrate that at a certain burst energy, transverse microcracks align with the linear polarization orientation. Furthermore, we show that the polarization state affects the modified glass separation, processing speed, efficiency, and quality.
Using laser-induced metal deposition technology, we demonstrate a cost-efficient and large-scalable method of transparent microscale metal electrode fabrication on glass. The novel electrodes are effective conductive layers, presenting a promising alternative to many electronic and electro-optic applications. This study discusses electrode formation and compares various designs. We analyzed the influence of femtosecond and picosecond laser pulse durations by varying the laser pulse duration and optimizing the repetition rate during laser processing. We found that picosecond pulses are more suitable for producing wider (about 31 μm) and higher (about 2 μm) electrodes. Meanwhile, femtosecond laser pulses are ideal for producing narrower (about 8 μm), lower (about 1 μm) electrodes. Furthermore, the optimized copper electrode design was tested in a multilayer smart window structure. It utilized a flexible conductive polymer, Poly(3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), in combination with the lithium perchlorate (LiClO4) electrolyte. We demonstrated the importance of proper layer alignment for achieving optimal smart window performance. Our findings suggest that transparent microscale electrodes formed by laser-induced metal deposition could contribute to the development of more sustainable and cost-effective smart devices.
Laser micro-machining is a rapidly growing technique to create, manufacture and fabricate microstructures on different materials ranging from metals and ceramics to polymers. Micro- and nano-machining on different materials has been helpful and useful for various biomedical applications. This study focuses on the micro-machining of innovative barbed sutures using an ultrashort pulse laser, specifically a femtosecond (fs) laser system. Two bioresorbable polymeric materials, namely, catgut and poly (4-hydroxybutyrate) (P4HB), were studied and micro-machined using the femtosecond (fs) laser system. The optimized laser parameter was used to fabricate two different barb geometries, namely, straight and curved barbs. The mechanical properties were evaluated via tensile testing, and the anchoring performance was studied by means of a suture–tissue pull-out protocol using porcine dermis tissue which was harvested from the medial dorsal site. Along with the evaluation of the mechanical and anchoring properties, the thermal characteristics and degradation profiles were assessed and compared against mechanically cut barbed sutures using a flat blade. The mechanical properties of laser-fabricated barbed sutures were significantly improved when compared to the mechanical properties of the traditionally/mechanically cut barbed sutures, while there was not any significant difference in the anchoring properties of the barbed sutures fabricated through either of the fabrication techniques. Based on the differential scanning calorimetry (DSC) results for thermal transitions, there was no major impact on the inherent material properties due to the laser treatment. This was also observed in the degradation results, where both the mechanically cut and laser-fabricated barbed sutures exhibited similar profiles throughout the evaluation time period. It was concluded that switching the fabrication technique from mechanical cutting to laser fabrication would be beneficial in producing a more reproducible and consistent barb geometry with more precision and accuracy.
The growing demand for flexible, high-quality fabrication of free-form micro-optics drives the development of laser-based fabrication techniques for both the shape formation and surface polishing of optical elements. In this paper, we performed a thorough and systematic study on fused silica glass ablation using 10 ps and 320 fs duration pulses. Ablation processes for both pulse durations were optimized based on the measurements of the removed material layer thickness and surface roughness, and by analyzing the topographies of ablated cavities to remove material layers as thin as possible with minimum surface damage. Our findings demonstrate higher process resolution and surface quality for femtosecond pulses. Ablation of pre-roughened glass reduced the minimal removable glass layer thickness well below the 1 μm mark for both pulse durations, improving the process resolution. The minimal removable glass layer thickness was 14 times smaller for the femtosecond pulses, with up to 4.5 times lower surface roughness compared to samples processed with picosecond pulses. On the other hand, results revealed faster glass removal rates with picosecond pulses. In the end, arrays of microlenses were fabricated with both pulse durations and subsequently polished with a CO2 laser. Results revealed higher performance of microlenses fabricated with femtosecond pulses, providing better focusing capabilities and lesser beam scattering. Finally, this study demonstrated the successful fabrication of free-form optical elements with femtosecond and picosecond pulses, demonstrating the versatility and the potential of laser-based techniques.