Direct-write micro- and nanostructuring laser technologies are very important for the fabrication of new materials and multifunctional devices. Using tightly focused femtosecond laser pulses one can produce submicrometer holes and periodic structures in metals, semiconductors, and dielectrics on arbitrarily shaped surfaces. The achievable structure size is not restricted by the diffraction limit. It is determined by material properties and the laser pulse stability. We report investigations of possibilities to use femtosecond laser pulses for nanostructuring of different materials.
Results of ablation of different materials by femtosecond and picosecond laser pulses are compared. Advantages and disadvantages of both laser systems are discussed. Two most important criteria, processing speed and quality of the fabricated structures, are addressed. High repetition rate picosecond lasers allow high speed cutting of thin metal foils and silicon wafers, whereas for micro-drilling it is more advantageous to use femtosecond laser systems.
Micro- and nanostructuring are very important for the fabrication of new materials and multifunctional devices. Existing photo-lithographic technologies can only be applied to a limited number of materials and used on plane surfaces. Whereas, microstructuring with femtosecond laser pulses has established itself as an excellent and universal tool for micro-processing, it is still unclear what are the limits of this technology. It is of great interest to use this technique also for nanostructuring. With tightly focused femtosecond laser pulses one can produce sub-micrometer holes and structures whose quality depends on the material. We present new results on nanostructuring of different materials with femtosecond laser pulses in an attempt to make this an universal technology, and discuss its reproducibility, and further prospects for quality control.
Investigations of possibilities for nanostructuring with femtosecond laser pulses of different materials are reported. The aim is to develop a simple laser-based technology for the fabrication of two- and three-dimensional nanostructures with structure sizes on the order of several hundred nanometers. This is required for many applications in photonics, for the fabrication of photonic crystals and microoptical devices, for data storage, displays, etc. Sub-wavelength structuring of metals by direct femtosecond laser ablation is performed. The band gap dependence of the minimum structure size for transparent materials is identified.
The development of a simple laser-based technology for the fabrication of two-dimensional nanostructures with a structure size down to one hundred nanometers is reported. The ability to micro- and nano-structure is very important for the fabrication of new materials and multifunctional microdevices. Photolithographic technologies can be applied only for plane surfaces. Using femtosecond laser pulses one can fabricate 100 nm structures on arbitrary 3D-surfaces of metals and dielectrics. In principle, the minimum achievable structure size is determined by the diffraction limit of the optical system and is of the order of the radiation wavelength. However, this is different for material processing with ultrashort laser pulses. Due to a well-defined threshold character of material processing with femtosecond lasers one can beat the diffraction limit by using tightly focused femtosecond laser pulses and by adjusting laser parameters slightly above the processing threshold. In this case only the central part of the beam can modify the material and it becomes possible to produce sub-wavelength structures. In this presentation, sub-wavelength microstructuring of metals and fabrication of periodic nanostructures in transparent materials are demonstrated as promising femtosecond laser-based nanofabrication technologies.
At the Laser Zentrum Hannover investigations of possibilities to use femtosecond laser pulses for direct ablative writing and microstructuring of solid materials have been started in 1995. Since then considerable progress in understanding and in the application of different femtosecond technologies has been obtained. At present, we are able to produce high quality microstructuring and large area patterning of solids with structure sizes between one and ten micrometers. By using tightly focused femtosecond pulses it is possible to produce even sub-micrometer structures. In this paper we pursue the goal to find and characterize the limits of femtosecond laser micromachining. Detailed investigations of possibilities to use femtosecond lasers for the sub-wavelength microstructuring of metals and for fabrication of periodic structures in transparent materials with the scale length of the order of several hundreds nanometers are reported.
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.
Possibilities to fabricate sub-micron structures in thin metal films, metal coatings, and glass substrates using femtosecond laser pulses are systematically studied. Structures are produced by direct femtosecond-pulse laser ablation of solid targets at atmospheric pressure. Tight focusing and imaging techniques are applied. Dependencies of the structure size on laser pulse energy and pulse number are investigated.
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.