Femtosecond laser systems offer a good solution for the creation of straight microcuts and grooves on macroscopic workpieces, as they are becoming more established in industrial applications. Although such linear ablation processes have been investigated and improved before, the main obstacle is still the long processing time. Increasing the processing speed by applying high pulse energies usually leads to a significant quality loss. Using high pulse repetition rates at low pulse energies would lead to the best results, but the repetition rate of commercially available laser sources is mostly restricted to one to several kilohertz. However, a systematic investigation of further relevant parameters enables the processing quality and speed to be optimized. To demonstrate these relations, cuts and grooves using different motion parameters and focusing strategies are presented at the example of metal and silicon samples. With regard to the focusing strategy, it is shown that by using linear focus shapes in the direction of the cut, cutting speeds can be increased while maintaining high edge qualities of the cuts and grooves. The presented results prove the potential of femtosecond lasers for high quality cuts in different industrially relevant materials.
Ultrafast lasers have become a promising tool for micromachining and extremely precise ablation of all kinds of materials. Due to the low energy threshold, thermal and mechanical side effects are limited to the bu micrometers range. The neglection of side effects enables the use of ultrashort laser pulses in a broad field of medical applications. Moreover, the interaction process based on nonlinear absorption offers the opportunity to process transparent tissue three dimensionally inside the bulk. We demonstrate the feasibility of surgical procedures in different fields of medical interest: in ophthalmology intrastromal cutting and preparing of cornael flaps for refractive surgery in living animals is presented. Besides, the very low mechanical side effects enables the use of fs- laser in otoralyngology to treat ocecular bones. Moreover, the precise cutting quality can be used in fields of cardiovascular surgery for the treatment of arteriosklerosis as well as in dentistry to remove caries from dental hard tissue.
Within the research project FEMTO, supported by the European Commission, a compact diode-pumped titanium:sapphire laser has been developed which matches the requirements of industrial systems, like compact dimensions and stable laser operation. To achieve this, the laser has been specially designed to be integrated directly into the machining system. For best process speed combined with optimal cutting quality, focus has been laid upon high repetition rates at moderate pulse energies. Typical average output powers are around 1.5W and repetition rates of up to 5 kHz. Accompanying to the laser development, a micro-machining system has been designed to meet the requirements of femtosecond laser micro-machining. In parallel to the machine development, machining processes have been investigated and optimized for different applications. The machining of delicate medical implants has been demonstrated as well as the machining system for general micro-machining of sensitive and delicate materials has been proven. Therefore, the developed machine offers the potential to boost the use of femtosecond lasers in industrial operation.
Femtosecond lasers have been proven as excellent tools for micromachining of solid targets. In contrast to other existing technologies, this method of laser processing allows structuring with highest precision by minimal damage to the adjacent material. The possibility of structuring nearly any kind of material gives access to new and innovative approaches in the field of optics. Periodic structures with dimensions on a micrometer scale are used for many photonic applications. Conventional ways of producing micrometers -scaled periodic patterns show the drawback of being limited by specific material properties, e.g. hardness, brittleness, which reduce the variety of machinable materials. However, femtosecond laser pulses offer great possibilities for the generation of periodic microstructures independent of the machined material. This includes the ablation of metals, dielectrics as well as the laser induced polymerization of photosensitive resins. Within this paper results on the generation of periodic microstructures by using femtosecond lasers are presented. Results of machining surfaces for applications like anodes and acceleration grids for streak camera tubes are presented, demonstrating a high potential for fs-laser micromachining in the field of optics.
Increasing miniaturization and integration of multiple functions into portable electronic devices and sensors ask for smaller electrical components. Conventional abrasive processes often reach their technological limit resulting in the demand for alternative technologies with increased precision and performance. Lasers have been proven to be a suitable tool for micromachining, but often suffering the disadvantage of heat or shock affected zones around the machined structures. To be feasible as an industrial solution, new approaches have to provide very high precision and process stability with minimal collateral damage. Presently, two different approaches for laser machining of semiconductor materials are being investigated. Although the interaction mechanism is completely different as described within this paper, both are regarded as promising technologies: ultrashort-pulse and short wavelength laser machining. Femtosecond laser machining has been used for a variety of applications, showing the advantage of non-thermal ablation of many kinds of materials. Due to the short pulse duration and the high intensities multi-photon absorption allows to overcome the bandgap of semiconductors while not affecting the bulk material. Due to the short wavelength excimer lasers as well as fluorine lasers provide the general ability to generate small spot sizes and emit photons with higher energies compared to the bandgap of the material, e.g. of silicon. Both technologies will be discussed and compared, and applications for micromachining of silicon will be presented.
Femtosecond laser systems have been proved to be effective tools for high precision micro-machining. Almost all solid materials can be processed with high precision. The dependence on material properties like thermal conductivity, transparency, heat- or shock sensitivity is strongly reduced and no significant influence on the remaining bulk material is observed after ablation using femtosecond laser pulses. In contrast to conventional laser processing, where the achievable precision is reduced due to a formed liquid phase causing burr formation, the achievable precision using femtosecond pulses is only limited by the diffraction of the used optics. Potential applications of this technique, a\including the structuring of biodegradable polymers for cardiovascular implants, so-called stents, as well as high precision machining of transparent materials are presented.
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