Recently, polycrystalline silicon thin film solar cells on glass are fabricated by a laser induced liquid phase crystallization (LPC) process. This study compares a new economic diode laser, emitting a line focus at 980 nm, with the 808 nm laser normally used concerning its absorption during LPC. We measured the optical constants of amorphous silicon by spectral ellipsometry and UV/VIS spectroscopy. Together with the literature data for crystalline and liquid silicon combined with numerical temperature simulations, we calculated the absorption during LPC and the overall power needed for successful crystallization. Solar cells prepared with both laser types show comparable crystallographic and optoelectronic characteristics. Concerning the economic advantages, the use of such a 980 nm diode laser system would be the choice for the potential industrial production.Polycrystalline silicon thin film solar cells on glass are fabricated by laser‐induced liquid phase crystallization. A new economic diode laser emitting a line focus at 980 nm is compared to the 808 nm laser normally used. Solar cells show comparable crystallographic and optoelectronic characteristics.

The use of laser technologies for the well-defined selective heating of wafers and thin film semiconductors for melt and non-melt rapid thermal processing (RTP) is an alternative way to fulfill the cost and performance goals of the 2nd and 3rd generation of photovoltaic products and other types of thin film electronics as well. A variety of efficient and reliable laser sources are available from UV to IR that can match the absorption characteristics of nearly any material layers and layer stacks. To make technical and economical use of these advantages the laser power has to be focused on the surface with a well-defined beam geometry and intensity profile. For fastest processing of e.g. Gen 5 to Gen 10 solar panels a linear scanning with a line or a rectangular beam profile is needed to achieve the required productivity. In addition to the beam geometry, the intensity distribution in scanning direction is an essential parameter for a controlled temporal heating and cooling profile of the thin film materials.

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.

LIMO has developed the new generation DIOCUT systems with an output power of 1.3kW and 2kW out of a 400µm core fiber NA0.12. Direct fiber coupled diode lasers have the potential to be most efficient in comparison to other laser approaches since it works without a brightness converter as a key component. Based on LIMÒs unique production technology special free-form refractive optics were developed that enable highest coupling efficiency and consequently a wall-plug efficiency including cooling system of 30% for the total laser system. To demonstrate the benefits of direct diode lasers in the kW power range, concepts, data of laser characterization as well as application results are presented in this paper. Cutting samples of various materials from steel to aluminum alloys up to 10mm were fabricated with high velocity. Reduced roughness of the cut edge (6mm stainless steel: Rz < 10µm) is one major cutting quality improvement.

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.

LIMO's unique production technology is capable to manufacture free form surfaces on monolithic arrays larger than 250 mm with high precision and reproducibility. Different kinds of intensity distributions with best uniformities or customized profiles have been achieved by using LIMO's refractive optical elements. Recently LIMO pushed the limits of this lens production technology and was able to manufacture first diffractive optical elements (DOEs) based on continuous relief's profile.Beside for the illumination devices in lithography, DOEs find wide use in optical devices for other technological applications, such as optical communications, laser technologies and data processing. Classic lithographic technologies lead to quantized (step-like) profiles of diffractive micro-reliefs, which cause a decrease of DOE's diffractive efficiency. The newest development of LIMO's microlens fabrication technology allows us to make a step from free programmable microlens profiles to diffractive optical elements with high efficiency. Our first results of this approach are demonstrated in this paper. Diffractive beam splitters with continuous profile are fabricated and investigated. The results of profile measurements and intensity distribution of the diffractive beam splitters are given. The comparison between theoretical simulations and experimental results shows very good correlation.