The polarization-and excitation-intensity-dependent photoluminescence of the negatively charged trion is investigated for ZnSe single quantum wells embedded in ternary and quaternary barriers. The measurements were performed in magnetic fields up to 11.8 T perpendicular to the quantum well. The spin-singlet state of the trion is clearly identified. In contrast to GaAs quantum wells, the increase of the trion binding energy through the magnetic field is found to be negligible, which is explained by the relatively small spatial extent of the trionic wave function in wide-band-gap materials. For magnetic fields beyond 7 T a resonance becomes stabilized that is identified as excited trion spin-triplet state because of its anticorrelation with the trion spin-singlet state behavior for increasing excitation energy.

Direct laser patterning of various materials is today widely used in several micro-system production lines like inkjet printing, solar cell technology, flat-panel display production, LEDs, OLEDs, semiconductors and medicine. Typically single-mode solid state lasers and their higher harmonics (e. g. 266, 355, 532 and 1064 nm) are used especially for machining of holes and grooves. The striking advantages of flat top intensity distributions compared to Gaussian beam profiles with respect to the efficiency and quality of these processes were already demonstrated. Here we will give an overview of parameters, methods and applications of Gaussian-to-top-hat beam shaping. The top hat field size can start from about 30 µm with no upper size limitation in the far field of the optics. Beam shaping for various wavelengths were realized with field geometries of squares, rectangles and circles. With LIMO's compact Gaussian-to-top-hat converter an inhomogeneity better than 5% contrast was reached. Special focus is put on the integration of Gaussian-to-top-hat beam shapers in fast scanning systems employing Galvo mirrors and a specially developed f-Theta lens to avoid destruction of the top hat profile within the scan field. Results with a 50x50μm² top hat size (inhomogeneity down to <10%) in a scan area of 156x156mm² are presented. The minimal distortions of the top hat observed within the scan area make LIMO's compact Gaussian-to-top-hat converter excellently suited for industrial scanning applications, e.g. for the processing of solar panels.

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Micro-lens arrays are widely used for beam shaping, especially beam homogenization of various laser sources. Monolithic arrays of cylindrical lenslets made of glass, semiconductors or crystals provide great advantages in laser applications, e.g. high efficiency, intensity stability and very low absorption. However, up to now, mainly symmetrical micro-lens surfaces are utilized in most applications due to design and manufacturing restrictions. The manufacture and application benefits of asymmetrical cylindrical-like micro-lens surfaces are enabled by LIMO's unique production technology. The asymmetrical shape is defined by uneven-polynomial terms and/or an asymmetrical cut-off from an even polynomial surface. Advantages of asymmetrical micro-lenses are off-axis light propagation, the correction of aberration effects or intensity profile deformations when the illuminated surfaces are not orthogonal to the optical axis. Additionally, the opportunities in simultaneous illumination from numerous light sources to one target are extended by just geometrical arrangement without the need for collinear beam alignment. First application results of such micro-lens arrays are presented for beam shaping of high power diode lasers. The generation of a homogeneous light field by a 100 W laser with tilted illumination at an angle of 35° is shown. A multi-kW line generator based on the superposition of over 50 diode laser bars under different illumination angles is demonstrated as well. Thus, laser material processing like plastics welding, soldering or annealing becomes much more convenient and less demanding regarding beam steering.

High power laser sources are used in a large variety of applications for materials processing. The most common are welding, soldering, cutting, drilling, laser annealing, micro-machining, ablation and micro-lithography. Beside the right choice of the suitable laser source adequate high performance optics for the generation of the appropriate beam profile are essential. Widely used geometries are square, rectangular light fields or light lines with homogeneous intensity distributions. The whole devolution from optical design and engineering to products and applications is demonstrated. LIMO has developed powerful software tools founded on Maxwell's Equations taking into account all important physical aspects of the beam shaping task. Various beam shaping principles, e.g. phase shifting for single-mode lasers, beam mixing for multi-mode lasers and other beam transformation schemes are discussed. Based on LIMO's unique production technology with computer-aided design free-form micro-lens surfaces can be structured cost-effectively on wafer-basis. Thus, the theoretically optimized surfaces can be transformed with high precision into a large range of materials. Typical products, their beam profiles and the respective application results are exemplarily shown for optical micro-lithography, micro-machining with Nd:YAG lasers and their harmonics as well as a-Si thin film annealing for flat panel display production.