It has been shown that micromachining of polymer materials using mode-locked, high repetition rate, 355nm picosecond
lasers is more efficient in respect to ablation rates and processing speeds, than using q-switched lasers at the same
wavelength and same average power level. In this study we present a systematic comparison of application results
obtained with q-switched nanosecond and mode-locked picosecond ultraviolet (UV) lasers. From the results, guidelines
are derived as to which laser type to use for best results depending upon material type and thickness. Additionally, recent
results obtained using a high power mode-locked UV picosecond laser - the Pantera<sup>TM</sup> - are described, along with
implications of how scaled-up power can significantly enhance processing efficiency in manufacturing environments.
Fluorine (F<SUB>2</SUB>) lasers emit at 157 nm, the shortest commercially available laser wavelength. Innovations such as NovaTube<SUP>TM</SUP> technology have resulted in powerful, highly reliable and cost effective F<SUB>2</SUB> lasers. This paper will discuss the most recent F<SUB>2</SUB> laser developments, resulting in repetition rates up to 1000 Hz and pulse energies in excess of 25 mJ. The industry now considers F<SUB>2</SUB> lasers to be the next step (after ArF at 193 nm) in key technologies such as lithography and micromachining.
The use of fluorine (F<SUB>2</SUB>) lasers, emitting at 157 nm, offers new possibilities for key applications demanding very high resolution and/or higher photon energy to expand the laser-processable material spectrum. Promising results have been achieved using F<SUB>2</SUB> lasers at 157 nm for micromachining of various materials that are very difficult to process at other laser wavelengths. This paper reports about new F<SUB>2</SUB> laser source developments and their efficiency in processing Teflon/Polytetrafluoroethylene and fused silica under moderate, uniform illumination conditions. Ablation rates and threshold parameters have been investigated. Scanning electron micrographs of the produced microstructures are presented.
Laser based rapid tooling techniques enable the completion of tools within a minimized period of time. Especially the controlled laser ablation process of metals or ceramics allows precise manufacturing along with a high surface accuracy of the parts. The reactive ablation mechanism of ferrous materials in oxygen atmosphere -- the chip removal - is described, as well as the optimization of the process parameters by systematical procedures. The processing results are limited with given radius of the interaction zone between the laser beam and the workpiece surface. Essential process-parameter is therefore the focus radius. This parameter, effectively being controlled by an adaptive optical mirror, strongly influences the process and thus the workpiece result. The laser ablation process characteristically offers a high flexibility concerning workpiece materials and geometries. In combination with the ability of processing even hardened steels without any tool wear laser ablation is predestined for the rapid tooling of metal forming tools like hot forging dies. Obtaining high workpiece accuracy along with short manufacturing times recommends the optimized ablation process not only for prototyping but for serial manufacturing as well.
The phenomenon of laser supported absorption (LSA) of CO<SUB>2</SUB> laser radiation is investigated with spatially and temporally resolved plasma spectroscopy in Argon as ambient gas at pressures of 1 - 10<SUP>5</SUP> Pa. A TE-CO<SUB>2</SUB> laser with a gas mixture of CO<SUB>2</SUB>/N<SUB>2</SUB>/He equals 1/4/4 at a total pressure of half an atmosphere is used. The pulselength of the TE- CO<SUB>2</SUB> laser is about 6 microsecond(s) at a mean power of some 100 kW. LSA-phenomena and material ablation processes are compared with that of a conventional TEA-CO<SUB>2</SUB> short pulse laser. It could be shown that longer pulses of less mean power make material ablation more efficient if the absorption wave becomes transparent within the pulse time of the laser. Maximum electron density of 2.5 (DOT) 10<SUP>17</SUP> and a temperature of 3 eV were measured 1.5 microsecond(s) after the beginning of the irradiation for an expanding aluminum plasma into vacuum.