Simulations and measurements on selective laser etching of display glasses are reported. By means of a holographic 3D beam splitter, ultrashort laser pulses are focused inside the volume of a glass sample creating type III modifications along a specific trajectory like pearls on a string. Superimposed by a feed of the glass sample a full 3D area of modifications is achieved building the cornerstone for subsequent etch processes. Based on KOH the modifications are selectively etched at a much higher rate compared to unmodified regions resulting in a separation of the glass along the trajectory of modifications. For gaining further insight into the etch process, we perform simulations on this wet chemical process and compare it to our experimental results.
A two-step laser-based concept is presented for cleaving glass substrates with tailored edges. In a first step beam shaped ultrashort laser pulses are used to modify the transparent material along chamfered or C-shaped edges. Secondly, thermal stress is applied close to the modified area by absorbing the radiation from CO2 laser. The tensile stress thus induced on the upper side of the glass leads to the actual release. The efficacy of our approach is demonstrated by presenting selected samples with tailored shaped edges and discussing corresponding edge qualities.
We report on the efficient use of high-energy, multi-millijoule ultrafast laser sources to operate well-known low-energy micro-machining applications such as surface texturing of transparent materials. A sophisticated optical system that employs micro-lens arrays is used enabling flexible beam splitting and thus parallel processing. Here, the number of foci can be varied ranging from a few ten up to a few hundred spots. As selected examples we will present efficient glass surface texturing using 8mJ and 200W of an industry grade ultrafast laser platform. Our micro-lens-array-based optical head is generating high-quality dimples on a (100 x 100)mm2 with filling factors above 25% area in less than 15s.
We report on the separation of glass substrates with customized edge contours including C-shapes. To achieve single-pass laser modifications along the entire contour geometry a processing optics is presented where a multitude of foci are simultaneously distributed inside a specific volume using a large-working-volume focusing unit. Tangential angles of the focus trajectory to the surface can be almost arbitrarily chosen and amount to even less than 45-deg in case of aiming for chamfered edges. After having induced laser modifications along the desired edge geometry, separation is done chemically in the present case. The glass articles, thus fabricated, meet the demands of the display industry in terms of bending strength and surface quality.
Based on the thin-disk laser architecture, TRUMPF has been developing and building high-power cw lasers for over two decades. The short pulse thin-disk lasers of the TruMicro 7000 series are employed in a wide range of industrial applications as well. With different wavelengths and pulse energies, the TruMicro 7000 series enables processes like cutting, structuring, and ablation of many materials.
Recently, TRUMPF introduced short pulsed UV lasers based on a disk laser medium for applications requiring high average powers in combination with nanosecond pulse lengths. With 180 W of average output power the TruMicro 7370 combines the highest average power of a solid-state laser with UV output and pulse energies of 18 mJ. With the solid-state platform, the lifetime is significantly increased compared to excimer lasers typically used for high power UV nanosecond applications.
Here, we present the latest development of this laser platform allowing for an increase of the laser power up to 400 W and the pulse energy to 40 mJ employing a cascading scheme for third-harmonic generation. By accessing TRUMPF’s elaborated disk-laser expertise, the new UV nanosecond laser TruMicro 7380 also provides enhanced pulse energy stability.
All these benefits of these short-pulse solid-state UV laser are predestining this platform for large-area applications as e. g. laser-lift-off of flexible OLED displays where average power and pulse energy can be translated into productivity by means of line-beam optics. The possibility of synchronizing up to twelve of these laser devices allows for even higher productivities.
In this work we present an ultrafast laser system distinguished by its industry-ready reliability and its outstanding flexibility that allows for real-time process-inherent parameter. The robust system design and linear amplifier architecture make the all-fiber series TruMicro 2000 ideally suited for passive coupling to hollow-core delivery fibers. In addition to details on the laser system itself, various application examples are shown, including welding of different glasses and ablation of silicon carbide and silicon.
The matchless properties of ultrashort laser pulses, such as the enabling of cold processing and non-linear absorption, pave the way to numerous novel applications. Ultrafast lasers arrived in the last decade at a level of reliability suitable for the industrial environment.1 Within the next years many industrial manufacturing processes in several markets will be replaced by laser-based processes due to their well-known benefits: These are non-contact wear-free processing, higher process accuracy or an increase of processing speed and often improved economic efficiency compared to conventional processes. Furthermore, new processes will arise with novel sources, addressing previously unsolved challenges. One technical requirement for these exciting new applications will be to optimize the large number of available parameters to the requirements of the application.
In this work we present an ultrafast laser system distinguished by its capability to combine high flexibility and real time process-inherent adjustments of the parameters with industry-ready reliability. This industry-ready reliability is ensured by a long experience in designing and building ultrashort-pulse lasers in combination with rigorous optimization of the mechanical construction, optical components and the entire laser head for continuous performance. By introducing a new generation of mechanical design in the last few years, TRUMPF enabled its ultrashort-laser platforms to fulfill the very demanding requirements for passively coupling high-energy single-mode radiation into a hollow-core transport fiber. The laser architecture presented here is based on the all fiber MOPA (master oscillator power amplifier) CPA (chirped pulse amplification) technology. The pulses are generated in a high repetition rate mode-locked fiber oscillator also enabling flexible pulse bursts (groups of multiple pulses) with 20 ns intra-burst pulse separation. An external acousto-optic modulator (XAOM) enables linearization and multi-level quad-loop stabilization of the output power of the laser.2 In addition to the well-established platform latest developments addressed single-pulse energies up to 50 μJ and made femtosecond pulse durations available for the TruMicro Series 2000.
Beyond these stabilization aspects this laser architecture together with other optical modules and combined with smart laser control software enables process-driven adjustments of the parameters (e. g. repetition rate, multi-pulse functionalities, pulse energy, pulse duration) by external signals, which will be presented in this work.
For many years, laser beam shaping has enabled users to achieve optimized process results as well as manage challenging applications. The latest advancements in industrial lasers and processing optics have taken this a step further as users are able to adapt the beam shape to meet specific application requirements in a very flexible way. TRUMPF has developed a wide range of experience in creating beam profiles at the work piece for optimized material processing. This technology is based on the physical model of wave optics and can be used with ultra short pulse lasers as well as multi-kW cw lasers. Basically, the beam shape can be adapted in all three dimensions in space, which allows maximum flexibility. Besides adaption of intensity profile, even multi-spot geometries can be produced. This approach is very cost efficient, because a standard laser source and (in the case of cw lasers) a standard fiber can be used without any special modifications. Based on this innovative beam shaping technology, TRUMPF has developed new and optimized processes. Two of the most recent application developments using these techniques are cutting glass and synthetic sapphire with ultra-short pulse lasers and enhanced brazing of hot dip zinc coated steel for automotive applications. Both developments lead to more efficient and flexible production processes, enabled by laser technology and open the door to new opportunities. They also indicate the potential of beam shaping techniques since they can be applied to both single-mode laser sources (TOP Cleave) and multi-mode laser sources (brazing).
Multi-megawatt ultrafast laser systems at micrometer wavelength are commonly used for material processing applications, including ablation, cutting and drilling of various materials or cleaving of display glass with excellent quality. There is a need for flexible and efficient beam guidance, avoiding free space propagation of light between the laser head and the processing unit. Solid core step index fibers are only feasible for delivering laser pulses with peak powers in the kW-regime due to the optical damage threshold in bulk silica. In contrast, hollow core fibers are capable of guiding ultra-short laser pulses with orders of magnitude higher peak powers. This is possible since a micro-structured cladding confines the light within the hollow core and therefore minimizes the spatial overlap between silica and the electro-magnetic field. We report on recent results of single-mode ultra-short pulse delivery over several meters in a lowloss hollow core fiber packaged with industrial connectors. TRUMPF’s ultrafast TruMicro laser platforms equipped with advanced temperature control and precisely engineered opto-mechanical components provide excellent position and pointing stability. They are thus perfectly suited for passive coupling of ultra-short laser pulses into hollow core fibers. Neither active beam launching components nor beam trackers are necessary for a reliable beam delivery in a space and cost saving packaging. Long term tests with weeks of stable operation, excellent beam quality and an overall transmission efficiency of above 85 percent even at high average power confirm the reliability for industrial applications.
The unique properties of ultrafast laser pulses pave the way to numerous novel applications. Particularly lasers in the sub-pico second regime, i.e. femtosecond lasers, in the last decade arrived at a level of reliability suitable for the industrial environment and now gain an increasing recognition since these pulse durations combine the advantages of precise ablation with higher efficiency especially in the case of processing metallic materials. However, for some micro processing applications the infrared wavelength of these lasers is still a limiting factor. Thus, to further broaden the range of possible applications, industrial femtosecond lasers should combine the advantages of femtosecond pulses and shorter wavelengths. To that extend, we present results obtained with a frequency doubled TruMicro 5000 FemtoEdition. We show that depending on the processed material, the higher photon energy as well as tighter focusing options of the shorter wavelength can open up a new regime of processing parameters. This regime is not accessible by infrared light, leading to a wider range of possible applications.
One of the most important issues in automotive industry is lightweight design, especially since the CO2 emission of new cars has to be reduced by 2020. Plastic and fiber reinforced plastics (e.g. CFRP and GFRP) receive besides new manufacturing methods and the employment of high-strength steels or non-ferrous metals increasing interest. Especially the combination of different materials such as metals and plastics to single components exhausts the entire potential on weight reduction. This article presents an approach based on short laser pulses to join such dissimilar materials in industrial applications.
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