PROCEEDINGS ARTICLE | September 12, 2008
Proc. SPIE. 7062, Laser Beam Shaping IX
KEYWORDS: Superposition, Homogenization, Lithographic illumination, High power lasers, Semiconductor lasers, Micro optics, Aspheric lenses, Laser cutting, Beam shaping, Spherical lenses
High power laser sources are used in a large variety of applications for material processing, such as ablation, welding,
soldering, cutting, drilling, laser annealing, micro-machining and deep-UV lithography. Using high performance optics
in the laser systems to generate the appropriate beam profile becomes a key factor for getting the best results and
throughput in an application field. Refractive micro-lens arrays made of glass, semiconductors or crystals provide great
advantages in laser applications, by improving efficiency, precision, intensity stability and performance.
With LIMO's unique production technology, free form surfaces on monolithic arrays exceeding 200 mm edge length can
be manufactured with high precision and reproducibility. Each lens of the array can be designed individually and can
also be shaped asymmetrically. The asymmetric shape is defined by
odd- and even-polynomial terms and/or an
asymmetric cut-off from a polynomial surface. Advantages of asymmetric micro-lenses are off-axis light propagation,
the correction of aberration effects, or the correction of the intensity profile deformations when the illuminated surfaces
are not orthogonal to the optical axis.
The applications 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 under an angle of 30°-50° 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.
Novel microoptical beam shapers in lithographic applications reduce the complexity of macrooptics in hyper-NA illumination systems. Extremely uniform intensity distribution can be created without using field lenses or by using simple spherical field lenses instead of complex aspheres.
