For many innovative applications a significant improvement in the homogeneity of the laser beam is a critical requirement when using semiconductor lasers. There are several different methods for the homogenization of laser
radiation. Homogenization using micro-cylinder lens arrays is a considerably elegant and compact solution. In this case
the incident laser beam is separated into partial beams by one or more micro-lens arrays. These partial beams are then
overlaid in the homogenization plane by the downstream optics. Depending on the arrangement and geometry of the
micro-lenses, this enables homogeneously illuminated lines, rectangles or squares to be generated. The major advantage of this solution lies in the increased freedom of adjustment to account for the initial beam profile, as well as the extremely compact design. In addition to a comparison of different homogenization principles the paper describes new approaches of homogenization via micro-lens arrays and compares the impact on the array performance by different manufacturing approaches.
New solid-state laser architectures require higher pump powers. In this paper we report the development of a new fibercoupled
diode laser capable of generating 15 kW from a 2 mm diameter fiber with a 0.22 NA, representing a brightness
of 220 mm.mrad at a single wavelength. In this design a special beam transformation technique has been developed to
achieve these specifications at a single wavelength without the wavelength combination technique employed in high
power diode lasers used in material processing applications. The specific laser presented here is at 938 nm with a
spectral bandwidth of 3.1 nm FWHM, but the same architecture is possible for wavelengths between 910 and 1060 nm.
High power single mode fiber lasers are an excellent tool for micro cutting applications. In order to manage the heat input into the material most micro cutting applications require pulsed operation of the laser. Temporal pulse shaping is a proven and enabling technology for many laser welding applications with flash lamp pumped lasers where typical pulse lengths are in the order of 0.1 to 10 ms. The excellent controllability of diode pumped fiber lasers enables pulse shaping during the cutting process with laser pulse length typically less then 0.1 ms. For laser micro cutting applications a small kerf width with small HAZ and good surface finish define the quality of the process. This paper shows the influence of the laser pulse shape on the cutting quality in stainless steel with diode pumped fiber lasers.
The fiber laser concept is proven technology for telecom applications where its single mode performance and reliability is essential. Newer generation diode-pumped fiber lasers are using pump diodes especially developed for telecom applications and therefore offer excellent controllability of the laser pulse length and pulse frequency. In the past years the output power of fiber laser increased steadily. This high power performance enables the fiber laser to serve applications like industrial marking. High power fiber lasers are now approaching power levels sufficient for micro cutting applications.
Using excimer lasers in DuPont's laboratories in Wilmington, we showed that a wide variety of nylon and polyester fabrics can be successfully irradiated to produce fabrics which combine the attractive visual and tactile aesthetics of cotton or wool fabrics with the durability, wrinkle resistance, and wash-and-wear performance of fabrics of 100 percent nylon or polyester. Extensive wear tests in such demanding end uses as bicycle pants proved that the desired aesthetic improvements were retained in use.
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