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Femtosecond technology, with its ultrashort light pulses, is an innovative laser technology that can be used for multiple applications, e.g., in industrial manufacturing, information and communication technologies, environmental technology and life sciences (medicine, biology, chemistry). This volume concentrates on the use of ultrashort pulses as a tool for ultraprecise material removal in manufacturing...
This Chapter gives an overview on various techniques employed today for ultrashort pulse generation. As an introduction to the concept of mode locking, it is briefly explained how phase locking the axial modes of a laser cavity can lead to the generation of short pulses. Both active mode locking, where an external signal modulates the radiation inside the cavity, and passive mode locking, where an...
This Chapter focuses on the generation of ultrashort pulses and their amplification to high energies in Nd:YVO4 and Yb:YAG bulk crystals. Particularly with regard to applications such as high-precision micromachining, we briefly describe why these materials can be a promising alternative for current systems mostly based on Ti:sapphire, and how the actual setup of a laser would benefit from the possible...
Reliable turn-key high-power ultrafast laser sources are required for a variety of applications in science, industry, and medicine. Fiber-based laser systems have the potential to fulfill this requirement. In this Chapter the possibilities of rare-earth doped fibers for the amplification of ultrashort pulses are discussed. Novel concepts to overcome limitations due to nonlinear effects are...
This Chapter deals with the generation and the amplification of ultrashort pulses in mode-locked oscillators and multipass amplifiers based on the thin-disk laser design. The first section covers soliton mode locking of a thin-disk laser employing semiconductor saturable absorber mirrors (SESAMs). Advantages over Kerr-lens mode locking and the prevention of Q-switching instabilities are also addressed...
Contrary to longer-pulsed laser irradiation, ultrashort laser pulses in the femto- and low picosecond-pulse duration domains are expected to be too short to interact directly with the material vapor they produce during ablation. Nonetheless, the very high intensities reached by focused ultrashort pulses cause a number of interaction phenomena of the pulses with the ambient atmosphere. The various...
In low-absorbing and low-scattering material, like biological tissue, optical breakdown can occur not only at the surface of the tissue but also inside the bulk. Here, different mechanical phenomena like cavitation and bubble development take place. In this chapter the basic interaction processes of ultrashort laser pulses with biological tissue like nonlinear effects during propagation through transparent...
In contrast to dielectric materials, metals are characterized by a high density of quasi-free electrons causing strong absorption of laser light from the beginning of the ultrashort laser pulse without the need of nonlinear absorption effects like multiphoton absorption. In a femtosecond timescale the energy transfer to the electrons can therefore be regarded as instantaneous. Their thermalization...
Several industrial applications use nanosecond laser pulses for micro-structuring of surfaces on macroscopic workpieces. The quality of the resulting structures, however, is limited due to the formation of recast that has to be removed by additional postprocessing. Experimental results presented here show that it is possible to avoid melt formation by shortening the pulse duration into the...
The use of ultrashort laser pulses for drilling of metals is highly promising with respect to reduced melt production and recast formation, as well as minimized heat-affected zones. It enables a machining precision far superior to that achieved by longer pulses, the full potential of which, however, can frequently only be reached using low laser fluence levels at the expense of processing speed....
For a number of years, diamond has been used as a material for cutting tools. Since conventional machining of diamond is difficult and expensive, laser cutting is considered a promising technology for future production of diamond-cutting tools. Experiments with nanosecond-lasers showed a tendency to crack formation in the material, especially in monocrystalline diamond. With femtosecond laser pulses...
In dentistry the specific interactions between ultrashort laser pulses and enamel/dentin of a tooth [1] or ceramic restoration materials [2] are advantageous due to minimal collateral damage. The femtosecond laser beam can be used as a tool to remove either decayed enamel/dentin – also named caries – or as a tool to remove ceramic from a bulk until the shape of an all-ceramic restoration is left...
Femtosecond photodisruption opens new pathways in refractive surgery due to its precise interaction mechanism with biological tissue. The quality of tissue processing allows correction of refractive errors and preparing donor and recipient tissue for keratoplasty with a much higher flexibility of what is known from the use of mechanical knives. In this chapter, the potential of ultrashort laser pulses...
The high precision of femtosecond laser ablation makes it an interesting tool for neurosurgical applications. The resection of arbitrary-shaped volumes of brain tissue can be of interest for the treatment of movement disorders. Fundamental studies of bovine brain-tissue ablation have shown precise cutting effects of femtosecond laser pulses with no thermal or structural side effects. If a large number...
Introduction:. Laser applications within the tympanic cavity area are fully accepted. Commonly used systems are CO2, argon-, KTP and erbium devices. The disadvantages are heat development and/or acoustic load of the inner ear. A new laser with ultrashort pulses was examined concerning its ablation characteristics and tested for possible applications in the tympanic cavity. Material and methods:...
Using high numerical focusing and pulse energies close above threshold for optical breakdown, disruptive effects can be generated in a range below the diffraction limit. This effect can be used to cut tissue with a precision at the cellular level. This kind of cell surgery offers a new field of experimental investigations in cell biology.
Nowadays the most intense lasers, working in the near-infrared wavelength range, are able to generate incoherent X-ray radiation from the soft X-ray region up to hard γ-rays. The X-ray radiation is not emitted by the laser itself but by a hot plasma that is produced by the interaction of the laser light with matter. Laser-produced X-rays all have in common an ultrashort duration, a small source size...
Using short laser pulses in metrological applications offers the possibility of very short observation times in combination with high accuracies. The high intensities allow for nonlinear techniques and very short pulses result in broad spectra as is necessary for white-light interferometric measurements. With respect to the demands of commercial devices the costs of the light sources had to be sufficiently...
Femtosecond laser pulses are close to industrial use. The advantages of ultrashort laser pulses for micromachining applications especially in the case of dielectric and biological samples down to pulse durations of 5 fs have been established. The current international standards of laser safety are primarily concerned with CW and pulsed lasers down to the nanosecond range. Therefore, human tissue...
Apart from primary hazards caused by the laser beam, ultrashort pulse lasers also pose secondary nonbeam hazards by gaseous and particulate laser-generated air contaminants or ionizing radiation. Though the emission rates for femtosecond-laser applications are remarkably lower than for conventional laser technologies (such as cutting, welding or cladding), the high respirability of particles can...
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