Using fly’s eye homogenizer has proven applicability in various fields, ranging from early-stage microscopy to state-of- the-art lithography. Hereby periodic lens arrays are commonly used to form a homogenous top -hat distribution. In turn, this periodicity can limit the attainable homogeneity by interference based micro - inhomogeneities. Furthermore, the positioning of the lens arrays results in small spot sizes directly at the lens surface, compromising functionality for large pulse energies. Here we present the challenges emerging due to the usage of non-periodic lens-arrays and introduce our design concept, suppressing interference based micro-inhomogeneities while being suitable for applications with large pulse energies.

Beam-shaping of homogeneous line profiles at ultra-violet wavelengths has wide applicability in the flat-panel display industry. Besides the well-established Excimer-Laser-based setups, diode-pumped-solid-state lasers with high repetition rates and comparatively small pulse energies have proven to be capable of providing a cost-effective alternative for different process steps e.g. Laser-Lift-Off or Solid-State-Laser-Annealing. We give a short summary about challenges emerging during the design of these system and demonstrate the generation of state-of-the-art laser-lines, offering a super-Gaussian, top-hat-shaped short-axis profile.

Long UV laser lines find application in crystallization of Si, lift-off of flexible OLED displays from assistance glass and other surface processing technologies. With the appearance of powerful and reliable pulsed UV DPSS lasers in the last years, many efforts are directed to the implementation of such lasers in the line systems instead of excimer lasers. For the processing with a high energy density, several DPSS lasers have usually to be coupled in a homogeneous line focus with 100 - 1000 mm length and FWHM of 20 - 40 mu m. We describe an advantageous line design approach based on anisotropic laser beam transformation, which improves beam quality for the narrow line axis and allows tight focusing with large depth of the focus. Solutions for tuning the line width are discussed.

Deflection and modulation of a laser beam for Q-switching or material processing can be realized in many ways. Today, one task is still the speed of these components. Especially for spatial pulse separation in ultrashort pulse laser applications the deflection must be faster (MHz). Promising solutions are deflectors based on the electro-optic effect.

Organic electronics is promising to be one of the groundbreaking technologies to revolutionize our everyday lives by including new functionalities into nearly any item. Cost is the most significant barrier, since new functionalities should not increase the price of the product dramatically. Roll-to-roll production is the solution to overcome the price barrier. In combination with integrated laser processes new possibilities are opened up for cost-efficient, versatile and high throughput manufacturing lines (Fig. 1).

Ultra-narrow line-shaped laser focuses are required for different material surface applications. We review the development of line-shaping optics for green DPSS lasers and report exemplary on several systems providing different line geometries and using different types of the lasers. These systems cover the line length range from 19 to 215 mm. One of the reported systems provides ultra-homogeny line-focus of 7.5 μm width and 215 mm length. It uses two rod Nd:YAG DPSS lasers and LIMO micro-optical anisotropic beam transformation technique to reach such a tight focusing and long depth of the focus. Contrarily another reported 200-mm green line is designed for bundling of eight Yb:YAG disc laser beams in a 100-μm wide line. The anisotropic beam transformation is not necessary for the shaping of this relatively broad line.

Optical Gaussian-to-tophat converters (g2T) that convert a Gaussian intensity distribution into a tophat profile find growing applications in different laser processing technologies. Usually, such refractive or diffractive g2T converters comprise of two or more optical components. For example, one aspherical component to form a tophat angular distribution followed by a Fourier lens that transforms it into the desired tophat intensity distribution in the focal plane. Here we report an optical design, which combines both optical functions in a single monolithic component. The component is designed and manufactured by LIMO as a free-form profile, providing the square tophat of 100-μm width at the distance of 125 mm. Compared to the traditional g2T-converters it is much more compact, easy to adjust, and less sensitive to alignment errors. In many industrial applications, not a single but multiple tophat foci are desirable for a fast parallel processing. For such applications we have developed a Gaussian-to-Tophat beam splitter. The beam splitting is done by a refractive-diffractive high-order grating with a smooth continuous pitch profile. Thanks to the smooth profile, such a Gaussian-to- Tophat beam splitter demonstrates very high efficiency of above 95% and high homogeneity between the diffraction orders.

Highly efficient beam splitters are important for a variety of high power laser applications. We prove different approaches like aperture and amplitude splitting for practicability for single- and multimode laser sources. Combining of micro- and macro-optical fabrication technologies allows novel monolithic free form splitting components with implemented segmented or stepless diffractive optical surfaces. The monolithic components are robust, compact and low weight and easy in handling. Here, we present two monolithic components: a segmented free form 1-to-17 beam splitter for fibre coupled lasers and a diffractive 1-to-11 beam splitter for single mode lasers with peak-to-peak pitch of 1.25mm and 0.8mm, respectively. The optical designs, the manufacturing of the prototypes as well as surface and performance measurements are reported. The prototypes from Fused Silica and Calcium Fluoride are designed for 532nm and 1064nm wavelength. Simulations show efficiencies larger than 98% and peak-to-peak non-uniformity below±3.2%. First laboratory results confirm efficiencies of < 95% and peak-to-peak non-uniformity of less than ±5%.

Ultra-narrow line-shaped laser focuses are required for different material surface applications. We discuss the optical solutions, like anisotropic transformation and homogenization of a multimode laser beam, and present examples of the line-beam shaping systems for industrial processing. These systems cover range from 13 to 400 mm of the line length by about 10 mu m line width. By the lengths above 200 - 300 mm the energy of several green lasers has to be bundled in the system.For a selective doping of solar cell emitter underneath the front contacts we have developed the optics, which provides instead of the continuous line-shaped focus a number of short line-segments (dashed line). Each of these segments is 14 mu m wide and 220 mu m (flat topped) long. The 17-segment line spans 33.5 mm and can be extended to cover a whole standard 6 '' Si wafer. The light source is an Yb:YAG 515 nm disc laser (TRUMPF).

Diffractive optical elements (DOEs) are of rising importance for many industrial laser applications, especially for laser beam shaping and laser beam splitting. Typically, such applications require high damage threshold of the diffractive optical elements as well as high diffraction efficiency. Usually DOEs with multilevel (step-like) phase profiles are made microlithographically and suffer from "quantisation" errors and scattering on profile derivative discontinuities. The step-like structure lowers the DOE damage threshold compared to the intrinsic material values.LIMO's microoptical technology is suitable for the production of high-precision free programmable continuous surface profiles in optical glasses, crystals and metals. It can be applied for manufacturing of microlens and micro-mirror arrays as well as for manufacturing of diffractive optics with continuous reliefs. Both the arrays and DOEs with continuous relief are suitable for high efficiency laser beam splitting. However, the design approaches to obtain a desirable solution for the corresponding continuous phase profiles are different.The results of the wave-optical simulations made by LIMO's own program and by VirtualLab software, and experimental studies for a 1 to 11 beam splitter with a continuous profile for the wavelength of 532 nm are presented. Continuous phase profiles for the DOEs were designed by a procedure based on the theory of beam splitting by a phase grating. Comparative theoretical and experimental studies were also done for splitting with a double-sided microlens array. For both types of beam splitting the efficiency can be very high (> 98%). The DOEs show especially high homogeneities of the resulting intensity distribution, however, they are much more sensitive to wavelength variations. The microlens arrays demonstrate even weaker ghost orders as the DOE splitters and their surface profiles are simpler. However, the efficiency and homogeneity suffer on interlens gaps.

In laser-based micro-machining, like high-speed patterning, perforation or dicing frequently the original laser beam is split into several beamlets to increase the throughput of the laser patterning system. Commonly diffractive optical elements with binary or multi-level step-like profiles are used which are produced by etching technique. This method typically results in optical efficiencies about 70-80%. Substantial scattering occurs at the profile steps which also give the tendency to lower damage threshold as compared to intrinsic material values. In contrast LIMOs unique production technology of programmable continuous free form surfaces on wafer basis is capable to produce kinoform beamsplitters with efficiencies > 95%. We report on 1:11 linear symmetric diffractive beam splitters at 1064 nm exemplarily. The efficiency for these 1:11 splitters is above 95%. The homogeneity between the different beams is typically about +/−5%. The design data, simulations with the measured surface profiles and experimental intensity measurements will be compared.

A new type of low-voltage planar electro-optical device for fast beam deflection is reported. It contains two EO modulators, both working as multimode waveguides. The geometry of the waveguides (ratio height to length) enables an efficient self-imaging of the entrance Gaussian mode. The EO modules are from LiNbO3:MgO with the thickness of 32 μm, length 9.75 mm, and width of 26 mm. The second stage works as an active phased array with 16 channels. The design provides a flat wavefront at the exit of the system despite the discrete phase shifts in the array channels. This makes a high steering resolution and optical efficiency possible. The full angle deflection range is of ±32•(1.27λ/D) by using of very low control voltages of 10 - 15 V. The voltages can be further reduced down to 5 V through constructive improvement of the EO-modules. The deflection range can be increased 16 times implementing a 3rd EO stage with a 16- channel EO-array. The deflector provides random access to the available angle states. The access time is limited generally by the capacity of the EO modules. It is of only about 0.1 nF in the reported design. We estimate that thanks to the low control voltage and electrical capacity of EO-modules a switching frequency of about 100 MHz may be possible with an advanced electronics. A relatively large face cross-section of about 1 mm2 will allow using the system with high power lasers and short pulse duration.

Diffractive optical elements (DOE) play an important role for laser beam shaping in industry, for example in lithography or parallel laser material processing. Typically such applications require high damage threshold and low background illumination (high contrast and efficiency). Usual DOE with binary phase (step-like) profiles are made microlithographically and suffer from substantial scattering on profile derivative discontinuities. That gives also tendency to lower damage threshold as compared to intrinsic material values. The LIMO approach is based contrarily on a proprietary, non etching material processing and is suitable for manufacturing of high-precision free programmable continuous surface profiles in optical glasses and crystals. We report on linear symmetric diffractive beam splitter 1:11 with high homogeneity and efficiency > 95% and discuss also other DOE designs. The design data, simulations with measured surface profiles and experimental intensity distributions are in very good agreement. Furthermore we report on a new type of optical attenuator composed from two DOE gratings. Its dynamic transmission range is 0.3% to 98%. The required lateral DOE shift is only 5 - 10 μm in the present design, so that the device can be very fast and applicable for dynamic intensity stabilization.

The aim of the study was to compare the histological results after complete osteotomies of the sheep tibia using either the prototype carbon dioxide (CO2) laser osteotome ‘OsteoLAS’ (n = 12) or an oscillating saw (n = 12). The laser parameters were as follows: wavelength 10.6 µm; energy of laser pulses 75–85 mJ; pulse duration 80 μs; pulse repetition rate 200 Hz; spot diameter 460 μm (1/e2 level); radiant exposure 45–51 J/cm2; peak irradiance 0.56–0.64 MW/cm2. Both groups were divided into two subgroups (n = 6), and the animals were killed after 4 weeks or 12 weeks, respectively. Light and fluorescence microscopy with semiquantitative analysis and histomorphometry were performed to compare bone healing. Charring-free laser osteotomies were possible up to a depth of 20 mm with the short-pulsed CO2 laser. The laser, however, required a significantly longer time to perform, and a wedge-shaped gap was present on the cis-cortex. After 4 weeks the osteotomy gaps were almost unchanged in both groups and filled with connective tissue. After 12 weeks the gaps were filled with newly formed bone in both groups. Primary gap healing was predominant in the laser group and longitudinal cortical remodelling in the control group. On a cellular level, no fundamental differences were observed for early and late stages of bone healing. Further research has to be focussed on improving the CO2 laser ostetome in order to reduce the long duration of the laser osteotomy and the necessity of creating a wedge-shaped cut in thick bones.

High power laser sources are used in various production tools for cutting, welding and hardening of metal parts and patterning, annealing and lithography of flat panel displays, solar cells and microelectronic devices. Beside the right choice of the laser source suitable high performance optical beam delivery and shaping systems are needed for generating the appropriate beam profile and intensity distribution are of high importance for the right processing speed, quality and yield. In addition to the typical laser processes with circular beam shapes LIMO has developed laser sources with line shaped beams for large area processing for e.g. crystallization and tempering of conducting and semi-conducting films on glass for FPD, PV and thermal processing of semiconductor wafer, coated float glass and sheet metal. Due to the high power density of several 100kW/cm2 and line length up to several hundred millimetres a treatment capacity of several m2 per minute and processing speeds up to 1 m/s can be achieved per laser head with typical scan & repeat processes. The use of multiple laser heads in one machine scales the productivity to the individual needs. The high scanning speed together with line widths of 0,01mm to 0,1mm is the basis for heating only a few microns of the surfaces layers and no costly cooling time is needed like with regular heating technologies. With this controlled surface heating even more sensitive materials can be processes like inks on polymers and paper for RFIDs, printed solar absorbers and coatings. For industrial applications equally important is an adequate understanding of the physics of the light-matter interaction behind the process. In advance simulations of the tool performance can minimize technical and financial risk as well as lead times for prototyping and introduction into series production. Based on this knowledge together with a unique free-form micro-lens array production technology and patented micro-optics beam shaping designs a number of novel production tool sub-systems have been built by LIMO: 1. a multi-kilowatt direct diode illumination modules for solar cell annealing, and crystallization; 2. a novel green laser beam line for the annealing of silicon thin films on glass; 3. a novel wavefront shaping optics that generates a top hat beam profile from a TEM00 high-power laser source for accurate thin film structuring. For each of these sub-system basic functionalities, design principles and performance results are presented with a special emphasis on resilience, cost reduction and process reliability.

Advanced laser crystallization of Si films for large flat panel displays requires a narrow very homogeneous focus with at least 235 mm length and high depth of focus. Earlier we have reported on the development and application of an ultranarrow (5-9 μm) homogeneous line-shaped laser focus of 60 mm length for sequential lateral solidification (SLS) of Si. Key element of our line shaping system is an anisotropic mode transformation of the 2nd green harmonic of a Nd:YAG laser beam and its following homogenization for the long focus axis. The design and built-up of a much longer "green line" requires innovative optical approaches and very high precision optical manufacturing. We analyze in detail different process requirements, their physical compatibility (e.g. line width vs. depth of focus) and practical feasibility. To reach high energy densities in the long lines we design optical schemas bundling up to 8 beams of separate lasers.

A new type of electro-optical (E-O) deflector which combines microoptical laser beam manipulations and electro-optical light wave phase control is presented. It consists of two stages, which include E-O arrays of LiNbO(3) as key components. The first stage forms a moveable "comb" of interference beamlets at the entrance to the second one. The second stage recombines the beamlets, reconstructs a plane wavefront and converts the translational movement of the comb to an angular deflection of the unified beam. Advantages of the concept as compared to other deflector types will be discussed. The laboratory results with He-Ne lasers are presented. The demonstrator is designed to provide a 63 mrad deflection with a diffraction limited resolution of 0.025 mrad. The technique is applicable for material processing with high-repetition- rate lasers, for laser projection, lidars and in other fields where high speeds and robustness are necessary or sources of vibration need to be avoided.

High power laser sources are used in various production tools for microelectronic products and solar cells, including the applications annealing, lithography, edge isolation as well as dicing and patterning. Besides the right choice of the laser source suitable high performance optics for generating the appropriate beam profile and intensity distribution are of high importance for the right processing speed, quality and yield.For industrial applications equally important is an adequate understanding of the physics of the light-matter interaction behind the process. In advance simulations of the tool performance can minimize technical and financial risk as well as lead times for prototyping and introduction into series production. LIMO has developed its own software founded on the Maxwell equations taking into account all important physical aspects of the laser based process: the light source, the beam shaping optical system and the light-matter interaction.Based on this knowledge together with a unique free-form micro-lens array production technology and patented micro-optics beam shaping designs a number of novel solar cell production tool sub-systems have been built. The basic functionalities, design principles and performance results are presented with a special emphasis on resilience, cost reduction and process reliability.

OBJECTIVE:The purpose of this study was to examine for the first time the feasibility of performing complete osteotomy of sheep tibia using a computer-guided CO2-laser osteotome, and to examine bone healing under functional loading.BACKGROUND DATA:Bone cutting without aggravating thermal side effects has been demonstrated with scanning CO2-laser osteotomy. Further research is necessary to develop a clinically usable laser osteotome, which may allow new types of bone surgical procedures.MATERIALS AND METHODS:The scanning parameters for performing tibial osteotomies were determined in preliminary ex vivo trials. Osteotomies were performed in the mid-diaphysis of sheep tibia using either the prototype laser osteotome (osteoLAS, study group; n = 12), or an oscillating saw (control group; n = 12). Both groups were divided into two subgroups each (n = 6), and the two groups were sacrificed after 4 and 12 wk. Radiographs were taken postoperatively and after 4, 8, and 12 wk to compare the course of bone healing.RESULTS:Laser osteotomies of sheep tibia up to a depth of 20 mm were possible without visible thermal damage to the bone. A sequential PC-controlled cut geometry with artificial widening of the osteotomy gap was required for a complete osteotomy. Both clinically and radiologically, the laser and control groups showed undisturbed primary gap healing. Bone healing was similar and undelayed after both laser osteotomy and osteotomy done by mechanical saw.CONCLUSIONS:Osteotomy of multi-layered bones with a scanning CO2-laser demonstrates clinical and radiological healing patterns comparable to those seen with osteotomy done by standard mechanical instruments. It is, however, a technically demanding procedure, and complete laser osteotomies of long bones are only reasonable in bones with a diameter <20 mm, which will likely restrict the use of this technique to bones 7-10 mm thick. Through the use of computer guidance, extremely precise osteotomies and sophisticated cut geometries are possible using this technique. For practical applications, precise control of the depth of laser cutting and easier manipulation of the osteotome are required.

Advanced laser crystallization of Si for flat panel displays demands a narrow line-shaped light focus with an ultimately high homogeneity. Key element of LIMO line shaping system is an anisotropic quality transformation of a multimode laser beam, which permits a very good homogenization for the long axis and tight focusing with a large depth of focus for the perpendicular high-quality axis. A prototype system has been built with a 90-W 532-nm DPSS laser. It provides a 59-mm long and down to 8 μm (FWHM) narrow focus with a residual inhomogeneity of only 1% (rms). The focus width is adjustable and its shape can be tuned from a quasi-Gauss to a top-hat intensity distribution. The depth of focus at 90% of the peak intensity DOF0.9I varies from 120 μm for a line width of 8 μm to 275 μm for FWHM = 14 μm. The design of longer lines is in progress at LIMO.