This PDF file contains the front matter associated with SPIE Proceedings Volume 8243, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Ultrafast picosecond lasers provide the gentle cold ablation required to selectively remove a 400 nm metal film from an unsupported ultra-thin polymer membrane without damaging the membrane substrate. Selected areas of the metal film are completely removed in an ablative lift-off process enabled by a single laser pulse. No damage to the polymer membrane is observed even for samples with the metal completely removed over a 50x50 mm area of the membrane. The 400 nm thick metal films can be patterned into arbitrary forms with feature sizes as small as 10 micrometers, and even submicron features are realistically possible with a modification to the processing system. The skin depth of aluminium in the THz regime is significantly shorter than the 400 nm metal thickness, so thicker metal films that are significantly more difficult to machine are not beneficial. As an example, thin-film wire grid polarizers for the THz regime are demonstrated. The thin-film polarizers are much easier and faster to fabricate than polarizers made by winding free-standing wires around a frame and their performance is very comparable. The thin-film polarizers also have the added benefit of a significantly higher potential for functionality deeper in to the THz spectrum due to their capacity for smaller feature sizes. More intricate patterns, such as meshes, can also be made to create THz bandpass filters. This method can be extended to cold ablation processing of multilayer films fabricated on thin polymer substrates for applications such as plastic electronics, displays and solar cells.

This work reports the preparation of polymer/TiO₂ nanocomposite by adding TiO₂ nanoparticles to the polymer matrices. TiO₂ nanoparticles can be effectively dispersed into the polymer. The refractive index of the nanocomposites can be tuned by increasing the concentration of TiO₂ nanoparticles. The prepared samples exhibit excellent optical transparency in the Vis-NIR region, i.e. at two-photon polymerization (TPP) processing wavelength, and can be used to write threedimensional structures by means of TPP. Structures with high refractive index have been produced with the novel ultrahigh resolution technology based on TPP processing of polymer/TiO₂ nanocomposites.

Grayscale photomasks are bi-layer metallic films consist of two thin layers of Bi-on-Indium or Tin-on-Indium. These films become controllably transparent by accurately varying laser power such that the optical density changes almost linearly from ~3 OD (unexposed) to <0.22OD (fully exposed). Previously, a direct-write raster-scan photomask system with a multi-line CW Argon-ion laser was used with feedback-controlled Gaussian beam to achieve 256-level grayscale masks. With the Gaussian laser spot, the feedback system was effective such that the average gray-level error reduced from ±4.2 gray-levels in an open-loop approach to ±0.3 gray-levels in a closed-loop approach. As most of the gray-level errors are due to the Gaussian beam profile making variations on the mask, a beam shaper was used to change the laser spot to a flat-top beam. Raster-scanning the mask using the flat-top beam helps further reduce the gray-level errors. Preliminary results show that the flat-top beam reduces gray-level fluctuations, and lines can be written with less overlapped area helping to have higher resolution masks. Having lines closer with smaller overlap suggests that accurately controlled laser power results in an accurate OD profile on the mask even with an open-loop approach. The accuracy of the laser power is also a reason for variations as it has only 1% accuracy. Some test patterns are written on the mask using open-loop and closed-loop approaches to demonstrate how accurate the gray-levels of the bimetallic thinfilms are using a flat-top laser beam.

Ultra short laser pulses in the ps or fs regime are used, when high requirements concerning machining quality are demanded. However, beside the quality also the process efficiency denotes a key factor for the successful transfer of this technology into real industrial applications. Based on the ablation law, holding for ultra short pulses with moderate fluences, it has been shown that the volume ablation rate can be maximized with an optimum setting of the laser parameters. The value of this maximum depends on the threshold fluence and the energy penetration depth. Both measures themselves depend on the pulse duration. For metals the dependence of the threshold fluence is well known, it stays almost constant for pulse durations up to about 10 ps and begin then to slightly increase with the pulse duration. The contrary behavior is observed for the energy penetration depth, it decreases over the whole range when the pulse duration is raised from 500 fs to 50 ps. In this paper we will show that the maximum ablation rate can therefore be increased by a factor of 1.5 to 2 when the pulse duration is reduced from 10 ps down to 500 fs.

Laser lift-off processes have been observed during structuring CIS thin film solar cells with ultra-short laser pulses, if a Mo film on glass is irradiated from the glass substrate side. To investigate the underlying physical effects, ultrafast pump-probe microscopy is used for time- and space resolved investigations. The setup utilizes a 660 fs-laser pulse at a wavelength of 1053 nm that is split up into a pump and a probe pulse. The pump pulse ablates the thin film, while the frequency doubled probe pulse illuminates the ablation area after an optically defined delay time of up to 4 ns. For longer delay times, a second electronically triggered 600 ps-laser is used for probing. Thus, the complete ultra fast pulse initiated ablation process can be observed in a delay time range from femtoseconds to microseconds. First experiments on the directly induced ablation of molybdenum films from the glass substrate side show that mechanical deformation is initiated at about 400 ps after the impact of the pump laser pulse. The deformation continues until approximately 15 ns, then a Mo disk shears and lifts-off with a velocity of above 70 m/s free from thermal effects.

Laser induced plasma can be used for rapid optical diagnostics of electronic, optical, electro-optical, electromechanical and other structures. Plasma monitoring and diagnostics can be realized during laser processing in real time by means of measuring optical emission that originates from the pulsed laser-material interaction. In post-process applications, e.g., quality assurance and quality control, surface raster scanning and depth profiling can be realized with high spatial resolution (~10 nm in depth and ~3 μm lateral). Commercial instruments based on laser induced breakdown spectrometry (LIBS) are available for these purposes. Since only a laser beam comes in direct contact with the sample, such diagnostics are sterile and non-disruptive, and can be performed at a distance, e.g. through a window. The technique enables rapid micro-localized chemical analysis without a need for sample preparation, dissolution or evacuation of samples, thus it is particularly beneficial in fabrication of thin films and structures, such as electronic, photovoltaic and electro-optical devices or circuits of devices. Spectrum acquisition from a single laser shot provides detection limits for metal traces of ~10 μg/g, which can be further improved by accumulating signal from multiple laser pulses. LIBS detection limit for Br in polyethylene is 90 μg/g using 50-shot spectral accumulation (halogen detection is a requirement for semiconductor package materials). Three to four orders of magnitude lower detection limits can be obtained with a femtosecond laser ablation - inductively coupled plasma mass spectrometer (LA-ICP-MS), which is also provided on commercial basis. Laser repetition rate is currently up to 20 Hz in LIBS instruments and up to 100 kHz in LA-ICP-MS.

Annealing of high-k metal-oxide (TiO₂, PZT, and BaTiO₃) Sol-Gel derived films by a 266nm laser pulse train was investigated. The TiO₂, PZT and BaTiO₃ Sol-Gel ink was used as precursors. A high repetition rate DPSS laser (up to 300 kHz, 25ns, 266nm, Coherent AVIA series), which produces an ns pulse train with a pulse delay of 3.3-33.3 ìs, was used as the heat source. The dense, hard and uniform metal-oxide thin films are fabricated on glass and Si substrates, respectively by laser annealing. The films on the glass substrate appear to be ploy-crystalline. The films on the Si substrate appear to be amorphous with nano-crystals embedded. These laser annealed films were characterized by AFM, SEM, TEM and Raman spectroscopy, respectively. The laser heating process was also numerically simulated.

When femtosecond laser pulses are focused inside a single crystal, anisotropic structural changes such as dislocation and cleavage occur along specific orientations. It can be interpreted that the anisotropic structural changes should be induced by transient stress after photoexcitation, such as a thermal stress and stress wave. To elucidate the mechanism of the laser induced structural changes inside crystals, we developed a novel time-resolved polarization imaging system, in which circularly polarized laser pulse was used as a probe light. The system enabled us to observe laser-induced transient stress distribution as well as the orientation after focusing fs laser pulses inside MgO and LiF single crystals. Based on the observation, we elucidated the relation between laser-induced transient stress distribution and anisotropic structural change inside the crystals.

Advanced lithography systems, such as ArF immersion lithography, have achieved a 32 nm node^{1, 2} and are already used in electronic device development. However, the advanced lithography systems are not suitable for fabricating nanostructures, such as rectangular cuboids, triangular prisms, chains, and nanogaps. These nanostructures are being used for various applications that include plasmonic solar cells^3-5 and photonic crystal lasers.^{6, 7} In this proceeding, we report an innovative lithography system appropriate for fabricating such nano-patterns with nanometric accuracy based on plasmon-assisted photolithography. The key technology is the two-photon photochemical reaction of a photoresist induced by plasmonic near-field light and propagating light in a photoresist film. This propagating light is a radiation mode from a higher order of localized surface plasmon resonances scattered by metallic nanostructures. The system does not induce nano-pattern deformation at the time of mask release. This system presents a simple alternative for producing nano-patterns instead of using nanoimprinting.

Just as CW and quasi-CW lasers have revolutionized the materials processing world, picosecond lasers are poised to change the world of micromachining, where lasers outperform mechanical tools due to their flexibility, reliability, reproducibility, ease of programming, and lack of mechanical force or contamination to the part. Picosecond lasers are established as powerful tools for micromachining. Industrial processes like micro drilling, surface structuring and thin film ablation benefit from a process, which provides highest precision and minimal thermal impact for all materials. Applications such as microelectronics, semiconductor, and photovoltaic industries use picosecond lasers for maximum quality, flexibility, and cost efficiency. The range of parts, manufactured with ps lasers spans from microscopic diamond tools over large printing cylinders with square feet of structured surface. Cutting glass for display and PV is a large application, as well. With a smart distribution of energy into groups of ps-pulses at ns-scale separation (known as burst mode) ablation rates can be increased by one order of magnitude or more for some materials, also providing a better surface quality under certain conditions. The paper reports on the latest results of the laser technology, scaling of ablation rates, and various applications in ps-laser micromachining.

We demonstrate fabrication of microfluidic chips integrated with optical waveguide embedded in a photostructurable glass for high-sensitive biochemical liquid analysis using a femtosecond laser. Femtosecond laser direct writing followed by annealing and successive wet etching in hydrofluoric acid solution resulted in the rapid manufacturing of microfluidic chips for the biochemical liquid concentration assay. By covering the internal wall of the microfluidic channel in the glass with low refractive index polymer, interaction between the liquid and incident analyzing light is enhanced. Therefore, the microfluidic chip enables us to analyze the low concentrations down to 7.5 mM of protein in bovine serum albumin. Such microfluidic chip realizes the efficient and high-sensitive concentration analysis of biochemical liquids at early stages of biochemical reactions.

For surface and 3D structuring the ultra short pulsed laser systems are mostly used in combination with galvo scanners. This work reports on the synchronization of the scanner mirror motion with the clock of the laser pulses, which is usually in the range of 100 kHz and higher, by a modification of the electronic scanner control. This synchronization facilitates the placement of the small ablation craters from single pulses with the precision of about 1 μm relative to each other. The precise control of the crater positions offers the possibility to test and optimize new structuring strategies. Results of this optimization process with respect to minimum surface roughness, steepness of wall, accuracy to shape and efficiency will be presented.

New laser processing strategies in micro processing of glass, quartz and other optically transparent materials are being developed with increasing effort. Utilizing diode-pumped solid-state laser generating nanosecond pulsed green (532 nm) laser light in conjunction with either scanners or special trepanning systems can provide for reliable glass machining at excellent efficiency. Micro ablation can be induced either from the front or rear side of the glass sample. Ablation rates of over 100 μm per pulse can be achieved in rear side processing. In comparison, picosecond laser processing of glass and quartz (at a wavelength of 1064 or 532 nm) yield smaller feed rates at however much better surface and bore wall quality. This is of great importance for small sized features, e.g. through-hole diameters smaller 50 μm in thin glass. Critical for applications with minimum micro cracks and maximum performance is an appropriate distribution of laser pulses over the work piece along with optimum laser parameters. Laser machining tasks are long aspect micro drilling, slanted through holes, internal contour cuts, micro pockets and more complex geometries in e.g. soda-lime glass, B33, B270, D236T, AF45 and BK7 glass, quartz, and Zerodur.

In this paper, micromachining inside of direct and indirect semiconductor, such as zinc oxide crystal (ZnO) and single-crystalline silicon(c-Si) using femtosecond laser pulses is successfully demonstrated. In the case of ZnO, oxygen vacancy or interstitial zinc was three-dimensionally induced by the near-infrared femtosecond laser pulse irradiation. The threshold energy for oxygen defect formation increased with increasing in a pulse width. The mechanism of the pulsewidth dependence of the damage threshold inside ZnO could be interpreted in terms of the excitonic Mott transition to the electron-hole plasma which depends on the electron plasma density induced by the laser irradiation. We have also successfully micromachined inside c-Si using infrared ultrashort laser pulses (λ = 1.24 μm). Optical microscope observation under an infrared lamp illumination indicates low density material or scattering structure was formed in the vicinity of the focal spot.

In order to minimize thermal load to the workpiece pico- and femtosecond lasers gain an increasing market share in industrial applications such as surface structuring or thin film selective ablation. Due to nonlinear absorption they are capable to process any type of material (dielectrics, semiconductors, metals) and provide an outstanding quality suppressing heat affects on the workpiece. In this paper, we report on results about surface engraving of metals (Al, Cu, Mo, Ni), semiconductor (Si) and polymer (PC) using a picosecond thin disk Yb:YAG-amplifier, which could be used in the picosecond regime as well as in the femtosecond regime by simply changing the seed laser source. In the picosecond regime the oscillator pulses, ranging from 10 to 34ps, can be directly amplified which leads to a quite simple and efficient amplifier architecture. On the other hand, a broadband femtosecond oscillator and a CPA configuration can be used in order to obtain pulse duration down to 900fs. We compare these results to recently obtained achievements using commercial femtosecond lasers based on Yb-doped crystals and fibers and operating at comparable output power levels, up to 15Watt. Finally, we have considered etch rate and process efficiency for both ps- and fs-regimes as a function of average power, of fluence and of intensity.

Various materials including aluminum (Al), monocrystalline silicon (c-Si) and alumina (Al₂O₃) were treated using two types of fiber lasers, one having femtosecond (fs) pulse width, and the other nanosecond (ns). The surfaces of these materials were characterized and evaluated by optical and electronic microscopy and surface roughness profilometry. Results obtained are correlated with the pulse energy delivery conditions, namely pulse width, average output power, pulse overlap and hatch step size. For metals, fs pulses produced shallow skin depth structuring, and contributed to structured ribbons on the surfaces of Al and c-Si, as well as conical pillars on c-Si. Ns pulses can be used to create distinct patterns or grainy structures, whose characteristics are strongly depending on the pulse overlap and pulse energy. In contrast to the relatively low roughness level encountered with the fs pulses, where the highest average arithmetic roughness of about 1.4 μm on c-Si, ns pulses produced significantly higher roughness values. The measured values for ns-textured surfaces had the range of 0.4-2.2 μm and 1.5-5 μm on c-Si and Al, respectively. Ceramics texturing require high-energy longer ns pulses due to the higher thermal thresholds required for ablation.

The recent development of ultrafast laser ablation technology in precision micromachining has dramatically increased the demand for reliable and real-time detection systems to characterize the material removal process. In particular, the laser percussion drilling of metals is lacking of non-invasive techniques able to monitor into the depth the spatial- and time-dependent evolution all through the ablation process. To understand the physical interaction between bulk material and high-energy light beam, accurate in-situ measurements of process parameters such as the penetration depth and the removal rate are crucial. We report on direct real time measurements of the ablation front displacement and the removal rate during ultrafast laser percussion drilling of metals by implementing a contactless sensing technique based on optical feedback interferometry. High aspect ratio micro-holes were drilled onto steel plates with different thermal properties (AISI 1095 and AISI 301) and Aluminum samples using 120-ps/110-kHz pulses delivered by a microchip laser fiber amplifier. Percussion drilling experiments have been performed by coaxially aligning the diode laser probe beam with the ablating laser. The displacement of the penetration front was instantaneously measured during the process with a resolution of 0.41 μm by analyzing the sawtooth-like induced modulation of the interferometric signal out of the detector system.

We report periodic nanostructure on solid material irradiated by scanning continuous wave (CW) laser. Long periodic nano strip grating lines (nano-SGL) formed, not in a spot, but along the trace of the beam scan, literally parallel to each other with a at trough between the strip lines. The period of nanostructure was varied with the laser power between 500 nm and 800 nm, which equals to wavelengths used for laser scanning of green and infrared lasers. Thermal simulation and Raman spectra indicated the temperature of target exceeded the melting temperature to form the periodic nanostructure on target materials.

A new approach to polish metallic freeform surfaces is polishing by means of laser radiation. In this technology a thin surface layer is molten and the surface tension leads to a material flow from the peaks to the valleys. No material is removed but reallocated while molten. As the typical processing time is 1 min/cm² laser polishing is up to 30 times faster than manual polishing. Reducing the roughness by laser polishing is achieved for several different materials such as hot work steels for the die and molding industries or titanium alloys for medical engineering. Enhancing the appearance of design surfaces is achieved by creating a dual-gloss effect by selective laser polishing (SLP). In comparison to conventional polishing processes laser polishing opens up the possibility of selective processing of small areas (< 0.1 mm²). A dual-gloss effect is based on a space-resolved change in surface roughness. In comparison to the initial surface the roughness of the laser polished surface is reduced significantly up to spatial wavelengths of 80 microns and therefore the gloss is raised considerably. The surface roughness is investigated by a spectral analysis which is achieved by a discrete convolution of the surface profile with a Gaussian loaded function. The surfaces roughness is split into discrete wavelength intervals and can be evaluated and optimized. Laser polishing is carried out by using a special tailored five-axis mechanical handling system, combined with a three axis laser scanning system and a fibre laser.

Many technical applications can benefit from the use of tribological structures in minimizing abrasive material wear and energy consumption without the integration of additional materials in a working assembly. Especially in lubricated friction systems, the tribological character can be significantly improved through the addition of oriented and repetitive microstructure. In this study, experimental tests are discussed for a small range of structure dimensions to verify the effect of optimizing the tribological contact performance. A nanosecond pulsed fiber laser is used to create various test structures with different sizes and form. The quality of the fabricated surface pattern, particularly form correctness, feathering and material modification effects of the ablated area is characterized and optimized. The influence of pulse duration, pulse energy and pulse delay using normal pulsing is presented and compared to various burst modes.

The patterning or figuring of fused silica, e.g. for optical components, requires sophisticated methods. The usage of laser radiation enables a fast as well as high-quality machining of transparent materials. In particular, the laser-induced front side etching (LIFE) method has an excellent potential for nm-precision structuring of dielectrics with a high surface quality. At the LIFE process the laser beam interacts with an absorber layer on top of the front side of the dielectric surface to be machined. Here, the LIFE of fused silica is studied by using laser radiation with a wavelength from ultraviolet to infrared with pulse durations from nanosecond to femtosecond. With all investigated laser sources a well-defined, nm-precise etching of fused silica by the LIFE process is possible. A linear dependence of the etching depth on the laser fluence can be found whereas etching depths up to 300 nm can be achieved. The optimal laser fluence ranges as well as the achievable etching depths are dependent on the laser radiation used for the LIFE process.

We demonstrate a facile and flexible method to fabricate close-packed microlens arrays (MLAs). Glass molding templates with concave structures are produced by a femtosecond (fs)-laser point-by-point exposures followed by a chemical treatment, and convex MLAs are subsequently replicated on Poly(methyl methacrylate) [PMMA] using a hot embossing system. As an example, a microlens array (MLA) with 60-μm rectangular-shaped spherical microlenses is fabricated. Optical performances of the MLAs, such as focusing and imaging properties are tested, and the results demonstrate the uniformity and smooth surfaces of the MLA. We also demonstrated that the shape and alignment of the arrays could be controlled by different parameters.

Applications of the parallel fs laser processing system to spatial control of material properties are presented. In the parallel laser processing system, multiple light spots are generated by modulating the spatial phase distribution of a laser beam with a spatial light modulator. When the light spots are sufficiently separated from each other or the energies of the excitation laser pulses are weak, there is little interaction between photoexcited regions. In many cases, no interaction between each photoexcited regions is preferable, because thermal energies and stresses from each photoexcited regions could influence the processing accuracy. On the other hand, we found that the interaction of thermal energies and transient stresses in a parallel laser processing inside transparent materials can be used for controlling the spatial distributions of material properties. In this paper, we show two applications of the interactions between multiple photoexcited regions. One is the control of the shape of the heat modification and distributions of elements inside glasses. Another is the modification of dislocation bands inside rock-salt crystals by the interference of stress waves generated at multiple spots.

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 μm 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 ìm wide and 220 μm (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).

Multi spot optics are used for parallelizing production and therefore enabling large-scale material processing. These elements split the beam into a periodic spot pattern with a defined grid and spot size. The challenge lies in the generation of a homogeneous envelope. Micro lens arrays offer a high flexibility in dimensions and shapes for the generation of different multi spot patterns. Within the paper we present the investigation of a micro lens array in a fly's eye condenser setup for the generation of homogeneous spot patterns. The principal functionality of the multi spot generator is shown and constraints of this setup are demonstrated. The multi spot generator is used for micro structuring of silicon with a nanosecond and a picosecond laser both at a wavelength of 355 nm. The multi spot generator splits the incoming beam into a linear spot matrix with 28 single spots. The ablation rate and structure quality using a multi spot generator are investigated compared to conventional treatment. It can be shown, that both ablation efficiency and structure quality can be increased by using a multi spot generator.

In this paper, it is demonstrated for the first time to our knowledge the use of a novel high-repetition rate 224 nm nanosecond Q-switched laser source for fiber Bragg grating fabrication. Results are compared with 213 nm a nanosecond laser source, recently reported for grating inscription. High index change are rapidly obtained using a phase mask technique in B/Ge doped fiber with a maximum average writing power of only 280 mW at 224 nm and 100 mW at 213 nm. Strong gratings can also be written in standard SMF28 fiber. Photosensitivity is shown to be due to single and two-photon absorption for SMF28 and B/Ge doped fiber, respectively.

During the recent few years picosecond lasers have been proved as a reliable tool for microfabrication of diverse materials. We present results of our research on structuring of thin films and surfaces using the direct laser writing and the laser beam interference ablation techniques. The processes of micro-pattering were developed for metallic, dielectric films as well as complex multi-layer structures of thin-film solar cells as a way to manufacture frequency-selective surfaces, fine optical components and integrated series interconnects for photovoltaics. Technologies of nano-structuring of surfaces of advanced technical materials such as tungsten carbide were developed using picosecond lasers as well. Experimental work was supported by modeling and simulation of energy coupling and dissipation inside the layers. Selectiveness of the ablation process is defined by optical and mechanical properties of the materials, and selection of the laser wavelength facilitated control of the structuring process. Implementation of the technologies required fine adjustment of spatial distribution of laser irradiation, therefore both techniques are benefiting from shaping the laser beam with diffractive optical elements. Utilization of the whole laser energy included beam splitting and multi-beam processing.

The photovoltaic (PV) industry requires higher efficiencies at lower manufacturing costs to become competitive with other power generation techniques. There are several approaches to increase the efficiency of solar cells. For example enhancements of the way photons are absorbed and how they generate charge carriers with low losses. Today, the so called first generation of photovoltaic devices based on crystalline silicon wafers are produced on a multi-GW-level. However, in most production lines there is only one laser process used to electrically isolate front and rear side of the cell. Lasers are predestined to generate local structures which will be required to manufacture high efficient solar cells. As an example we will show results on the interaction of ultra short laser pulses with dielectric films on silicon. Second generation photovoltaic modules are based on thin films. These modules are monolithically interconnected by laser scribing of the films. Tools for amorphous silicon are well established, while there are a lot of challenges to scribe CIGS layers. Within this paper we will show new results on the temporal evolution of a laser induced "lift-off" process to scribe the molybdenum back electrode.

Recent developments in Cu(In,Ga)Se₂ (CIGS) thin film photovoltaics enabled the manufacturers to produce highly efficient solar modules. Nevertheless, the production process still lacks a competitive process for module patterning. Today, the industry standard for the serial interconnection of cells is still based on mechanical scribing for the P2 and P3 process. A reduction of the non-productive "dead zone" between the P1 and P3 scribes is crucial for further increasing module efficiency. Compact and affordable picosecond pulsed laser sources are promising tools towards all-laser scribing of CIGS solar modules. We conducted an extensive parameter study comprising picosecond laser sources from 355 to 1064 nm wavelength and 10 to 50 ps pulse duration. Scribing results were analyzed by laser scanning microscope, scanning electron microscope and energy dispersive X-ray spectroscopy. We developed stable and reliable processes for the P1, P2 and P3 scribe. The best parameter sets were then used for the production of functional mini-modules. For comparison, the same was done for a selection of nanosecond pulsed lasers. Standardized analysis of the modules has shown superior electrical performance of the interconnections and confirmed the feasibility of a dead zone width of less than 200 ìm on an entire mini module.

Recently, PCB(Printed Circuit Board) is required more high precision, function and miniaturization for advanced electronics, display, semiconductor and packaging, etc. and this complex PCB needs cutting, repair, trimming and structuring, etc. So, we make complex machine that is possible this all PCB processing and test PCB material processing using developed machine. This machine consists of UV nano-second pulse laser, power controller(self-developments), probe stage for trimming, auto focusing and scanner. The power controller is possible to monitor real-time power and adjust precision laser power. Using various parameters such as laser power, scanning speed, repetition rate and pulsed overlaps can obtain for process result having high precision and speed.

The fast development of laser technology requires creating a specialistic resource base for laser production certification together with radiant power (energy) measuring devices [1, 2]. This need becomes of special importance at the time when commencement of laser production at quantum points, holes and wires, whose dynamic scope of power and energy starts from counting individual photons up to tens of kilowatts (kilojoules), and the spectrum from ultraviolet to a near infrared [3]. Such are the characteristics of currently accessible laser radiation sources, used both for laser position finding and in other spheres of laser construction. Scattered radiation receivers, which are used in conditions of registering extremely low levels of radiant power, require examining of their metrological characteristics in order to define the value of their uncertainty. Elaborating such a laser set will constitute a basis for further improvement of a system for securing uniformity of measurements of basic energy parameters, characteristic for laser radiation. A set of standards now under elaboration will allow for the certification of all kinds of lasers. Choosing the optimum scheme for the elaboration of a new standard would enable the creation of a standard encompassing: a complete relation to ISO 11554- 2008 norms; with high accuracy of reproducibility of the volume of power unit (relative expanded uncertainty ~0,02%) and transmitting its volume; with an expanded power range P=1,0•10-²÷2,0[W] and with an expanded spectrum range λ=0,3÷10,6[μm]; with repeatability of measurements' results.

Due to its electro-optical, acousto-optical, ferroelectric, piezoelectric and nonlinear-optical properties lithium niobate is a material of high technological relevance. Thus, patterning of LiNbO₃ surfaces by laser light may significantly influence the performance of micro-optical devices made of this material. Here, we report on the generation of self-organized nanostructures on surfaces of unpoled LiNbO₃ crystals using tightly focused sub-15 fs pulsed Ti:Sapphire laser light (centre wavelength 800 nm, bandwidth 120 nm, repetition rate 85 MHz) at sub-nanojoule pulse energies. With the LiNbO₃ surface immersed in oil intensities close to the ablation threshold resulted in the formation of shallow ripples of 5 - 25 nm in height appearing at a periodicity of approximately 220 nm. The ripples were generated by local melting and resolidification of LiNbO₃ involving minor admixture of hydrocarbons. At intensities well beyond the ablation threshold the LiNbO3 surfaces were patterned densely with tiny cones of 100 - 500 nm in height featuring diameters of a few hundred nanometers. Moreover, lines scanned inside the LiNbO₃ crystals resulted in refractive index changes along the laser traces. In contrast, with the LiNbO₃ surface in air or water, ablation was not observed even at prolonged exposure due to aberrations of the focal spot.

Carbon fiber reinforced plastics (CFRP) composite material, which is expected to reduce the weight of automotive, airplane and etc., was cut by laser irradiation with a pulsed-CO₂ laser (TRUMPF TFL5000; P=800W, 20kHz, τ=8μs, λ=10.6μm, V=1m/min) and single-mode fiber lasers (IPG YLR-300-SM; P=300W, λ=1.07μm, V=1m/min)(IPG YLR- 2000-SM; P=2kW, λ=1.07μm, V=7m/min). To detect thermal damage at the laser cutting of CFRP materials consisting of thermoset resin matrix and PAN or PITCH-based carbon fiber, the cut quality was observed by X-ray CT. The effect of laser cutting process on the mechanical strength for CFRP tested at the tensile test. Acoustic emission (AE) monitoring, high-speed camera and scanning electron microscopy were used for the failure process analysis. AE signals and fractographic features characteristic of each laser-cut CFRP were identified.

We have developed a technique, optical hyperdoping, for doping semiconductors to unusually high levels and endowing them with remarkable optoelectronic properties. By irradiating silicon (Si) with a train of femtosecond laser pulses in the presence of heavy chalcogen (sulfur, selenium, and tellurium) compounds, a 100-300 nm thin layer of Si is doped to nonequilibrium levels (~1 at. %). Hyperdoped silicon exhibits near-unity photon absorptance from the ultraviolet (λ < 0.25 μm) to the mid-infrared (λ > 2.5 μm), even though crystalline silicon is normally transparent to wavelengths λ > 1.1 μm due to its band gap at 1.1 eV. Concurrent to doping, we are also able to use fs-laser irradiation to create light-trapping surface textures on the micro- and nanometer scales. Together, optical hyperdoping and surface texturing represent a route towards high-performance thin film photovoltaic devices.

Huge numbers of 2D- or 3D- nanostructures can be generated by interfering ultra-short pulse laser processing in a single shot. Unit structures are nanowhiskers, nanoneedle, nanobump, nanomesh of metal. The distribution of these nanostructures are according to interference pattern, which can be controlled and designed by the number of beams, correlation angle, amplitude ratio and phase shifts between the beams. In this paper, we simulated the interference pattern with different combinations of these parameters. Our technique is useful for fabrication of metamaterials, in which designed unit structures are in designed periodic patterns.

Enhanced optical field close to nano-dielectric spheres excited by a femtosecond laser enables high-throughput nano-crater patterning. With spheres larger than the incident wavelength, the focused far field is well known in optics to be governed by micro-lens, while the enhanced near field with spheres smaller than or equivalent to the incident wavelength is dominated by the resonant Mie-scattering. The crater fabricated by the near-field nano-lens is much shallower than by the micro-lens. Revealing the largest crater depth relative to the diameter will advance the smart applications for nanotribology, nano-sensors and nano-biomedicine. Here, we study the aspect ratio (the depth profile in the substrate relative to the diameter of the intensity profile on the surface of the near-field intensity distribution in the substrate). It is because the fabricated nano-crater depth is empirically determined by the near-field intensity distribution. A maximal vertical intensity profile is found as a function of refractive index and sphere diameter. The dielectric spheres ranging from 400 to 1000 nm diameter on the Si substrate are studied at 800 nm wavelength. Using a sphere with the smaller refractive indices, the larger aspect ratio is achieved. However, a maximal optical intensity is sacrificed for the high aspect ratio. Largest aspect ratios for the near-field nano-patterning range from 3.0 through 4.2 using available spheres with refractive indices of from 1.4 to 3.0. We also consider the difference of the enhanced optical intensity distribution between the systems consists of a single isolated dielectric sphere on a silicon substrate and that consisting of mono-layered hexagonal dielectric sphere array on a silicon substrate.