FOCUS
MANUFACTURING with short pulse lasers
with a focused USP laser. A galvanometric scanner is typically used to scan the surface and create specific patterns. Alternatively, Laser- Induced Periodic Surface Structures( LIPSS) can be formed when the material’ s surface is melted, leading to self-organized structures smaller than the laser spot( see figure 3). The quasi-periodic structures that form are oriented based on the incident polarization, with periods comparable to or smaller than the laser wavelength.
Surface texturing alters a range of physical properties, including:
• Wettability:( Super-) hydrophobic or( super-) hydrophilic surfaces can be created using the lotus effect. Wettability gradients can even be used to manipulate the movement of micro-droplets.
• Color: Grating effects produce iridescence, similar to the colors seen on butterfly wings.
• Non-adhesion properties: These improve the lifespan of industrial molds.
• Drag reduction: Riblet structures on surfaces reduce drag for objects moving through fluids, such as aircraft, boats, submarines, or rockets, enhancing energy efficiency.
• Biocompatibility: Certain textures exhibit antibacterial properties, while others promote cell growth.
• Absorption and emissivity: Specific textures can trap light, creating ultra-dark surfaces with high thermal emissivity.
These functionalizations can be applied to a wide range of materials, from metals and polymers to ceramics and glasses.
Figure 2. Illustration of thermal accumulation depending on the USP laser repetition rate.
magnitude higher in regions irradiated by the laser. This enables the fabrication of highly complex shapes through subtractive manufacturing, following three-dimensional laser scanning of the material to be removed.
A notable application involves Through-Glass Vias( TGV), which are micrometer-scale holes drilled through glass plates to separate and connect multiple electronic circuits via conductive material filling. TGVs can be created through direct laser ablation or, more efficiently, via laser-induced etching. Non-diverging Bessel-like beams allow for the production of long TGVs with high precision.
USP lasers also enable glass welding. By focusing the laser beam on the interface between two materials, multiphoton absorption occurs, locally melting the glass. This technique can join different types of glass— even those with varying thermal and mechanical properties( e. g., thermal expansion)— as well as glass
with metals, semiconductors, and ceramics. Applications include optoelectronic component packaging, microfluidic systems, and other scenarios where adhesives are unsuitable due to high temperatures or degassing concerns. While fused silica may develop micro-voids that scatter light, most other glasses achieve excellent transparency after welding.
USP lasers are also used for precision glass cutting. The focused beam creates micro-cracks within the material, guiding controlled fracture propagation. Another key application is the inscription of waveguides in the volume of the glass by modifying the refractive index. This technique can also produce Bragg gratings and other complex optical filters.
FUTURE CHALLENGES One of the primary challenges is increasing throughput to process large mechanical components efficiently( see figure 4). High-power laser sources are already available, and process parallelization can be achieved using multibeam arrays. As example, it is a requirement for lithium-batterie electrode texturing. These arrays can be generated using static diffractive optical elements, multi-plane light conversion beam shapers or dynamic spatial light modulators( e. g., liquid crystal-based).
High-speed scanning can be accomplished with polygonal mirrors, reaching speeds of up to km / s, while real-time pulse energy control is enabled by high-speed triggers. With repetition rates now exceeding 10 MHz and commercially available burst modes up to GHz, process optimization
3D MANUFACTURING OF DIELECTRIC MATERIALS In transparent materials, structuring is not limited to the surface but extends into the volume. Glasses can be etched through direct ablation or laser-induced etching. In the latter case, wet etching— using hydrofluoric acid, for example— is employed. The wet etching rate is several orders of
Figure 3.( left) color effect by surface texturing achieved by( right) Laser Induced Periodic Structures( LIPS) at smaller scale( zoom).
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