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Cutting thick plates is affected not only by the laser power but also by the cut kerf width and the melt flow dynamics that determine the ejection of the molten material. Employing the same laser beam intensity distribution for various thicknesses is the limiting factor when cutting thicker plates. This paper investigates fiber laser fusion cutting of 25 mm thick aluminum with dynamic beam shaping (DBS). While both static and longitudinal dynamic intensity distributions fail to cut this thickness with a 4 kW laser power, a cut through is achieved using annular and elliptical intensity distributions. However, an improvement of 45% in cutting speed can be achieved using an elliptical intensity distribution compared to an annular one. In order to understand the effect of the beam shape, an infrared thermal camera is used to study lateral heat propagation when using different process parameters. Moreover, to analyze the melt flow when changing the DBS frequency, high-speed imaging is utilized to observe the molten material inside the cut kerf. Finally, the cut edge quality is investigated for different cutting conditions. [ABSTRACT FROM AUTHOR]

The ultraviolet (UV) wavelength regime is attracting increasing attention because of its growing demand in semiconductor lithography, spectroscopy, and imaging applications owing to its high spatial resolution and high photon energy. However, beam shape control, beam delivery, and wavefront manipulation of UV laser beams usually require highly dedicated optics because of the strong UV absorption of most optical materials and the high surface precision required for tailoring short wavelengths, thus limiting a broader application of UV wavelengths. Here, we demonstrate a novel dynamic UV harmonic beam pattern control by manipulating the near-infrared (NIR) wavefront of the fundamental wavelength of a femtosecond pulse laser. The temporal and spatial coherences in an optical harmonic generation are known to be well preserved. Therefore, the spatial beam distribution of UV harmonic beams (λ = 400 and 266 nm for second and third harmonics, respectively) could be readily controlled by tailoring the wavefront of the driving infrared (IR) beam, and this approach can be expanded to higher-order harmonics in the vacuum ultraviolet (VUV) or extreme ultraviolet (EUV) regimes. Moreover, this enables fast polarization-sensitive UV beam switching at a speed of 6.7 frames/s in a depth-resolving manner. To efficiently separate the UV beam from the strong fundamental IR background beam, a non-collinear harmonic generation configuration is introduced. This facile dynamic UV beam control technique enables arbitrary wavefront control of UV laser beams for high-precision laser patterning, polarization-sensitive encryption, and 3D holograms.

Modern fiber-bound or mirror-optical manipulation of the laser beam to adapt intensity distribution in the area of the weld pool dominate recent developments for process stabilization and thus for quality improvement, for example for e-mobility applications. Especially the use of beam manipulation for material-oriented adaptation of the welding process appears very promising. In this paper, the new opportunity of high dynamic beam shaping (DBS) for the prevention of hot cracks in age-hardenable aluminum alloys is described in order to avoid the otherwise necessary addition of filler metal. The results from laboratory experiments show that, depending on the joint geometry and the Al-alloy, typical hot crack formations in the weld metal will be almost completely suppressed. Furthermore, for the first time it is possible to overcome metallurgical limitations in laser beam welding with remote optics by using this intensity-based approach. [ABSTRACT FROM AUTHOR]

Dynamic beam shaping brings a large potential for the laser cutting process by increasing the cutting speed and improving the cut edge quality. However, laser beam oscillation is almost exclusively realized with 2-mirror galvanometer scanners that limit the industrial implementation of the technology. Within this work, a new concept platform based on a single-mirror scanning system with a 4 kW fiber laser is tested for cutting of 12 mm thick plates in different materials. Technology knowledge transfer from existing datasets with common 2-mirror scanners has been used to speed up the optimization of the novel system. The proposed solution is able to substitute conventional deflection mirrors and can be easily integrated into the optical beam path of existing industrial machines. This paper introduces the advanced laser cutting process possibilities and experimentally demonstrates the dynamic beam shaping performance compared to the static beam reference system. [ABSTRACT FROM AUTHOR]

Further improvement of quality and productivity are some of the most relevant laser cutting process challenges. One way of affecting the process performance is manipulating the laser beam intensity distribution. Within this work, the feasibility of enhancing the cutting speed and edge quality using dynamic beam shaping in 4 kW fiber laser cutting of 15 mm stainless steel is investigated. Moreover, in order to evaluate the effect of dynamic beam shaping parameters on the process zone, a simplified thermal simulation model is introduced. As a result, the effect of longitudinal beam oscillation on the cutting efficiency is studied experimentally and explained using numerical calculation. The obtained results have shown a significant improvement for laser fusion cutting compared with a static top-hat intensity distribution. In particular, the cutting speed can be increased up to 45 % with considerably better quality. Finally, further steps to optimize the dynamic beam shaping technology for laser cutting applications are proposed. [ABSTRACT FROM AUTHOR]

The latest research on applying beam oscillation in laser beam fusion cutting revealed significant process improvements regarding speed and quality. The reason for this increasing process efficiency remains unexplained; however, theoretical investigations suggest the change in energy deposition (respectively heat conduction) as the cause. The present paper aims to analyze the energy deposition by a novel temperature measurement method. For this purpose, a conventional laser beam cutting setup was equipped with beam oscillation technology and a high-speed temperature measurement setup. Various characteristics of the temperature distribution in the process zone (spatial and temporal resolved temperature profiles, maximum and average values, as well as melt pool size) were evaluated for different conditions of beam oscillation (amplitude, frequency, cutting speed). Additionally, the geometrical properties of the process zone, defining the absorptivity have been measured. The comparison with static beam shaping reveals strong temperature volatility, which is induced by the way of energy deposition and an improved absorptivity over a substantial part of the cut front, with the overall result of enhanced heat conduction. For the first time, changed mechanisms applying beam oscillation instead of static beam shaping have been experimentally identified. Based on these measurements, a previously developed explanatory model was not only confirmed but also extended. [ABSTRACT FROM AUTHOR]

The latest research on laser beam fusion cutting (LBFC) with static beam shaping have shown a limitation in the quality of cut parts for thick steel plates (> 6 mm) when using solid state lasers. The approach of dynamic beam oscillation has recently shown to be capable of overcoming this challenge, allowing to increase the cutting speed as well as improving cut edge quality beyond the state of the art. The present paper investigates the influence of longitudinal, linear beam oscillation in LBFC of 12 mm mild and stainless steel plates by analyzing different parameters as cutting speed, burr, surface roughness, heat affected zone (HAZ), and recast layer. Reasons for the observed process improvements compared to static beam shaping have been discussed. The adjustment of the energy deposition and interaction time of the laser beam with the material found to be most relevant for optimizing the LBFC process. In particular, for beam oscillation, a gradual energy deposition takes place and increases the interaction time. This reduces the heat input in terms of HAZ and recast layer by more than 50%, resulting in high cut edge quality and more than 70% faster cutting speed. [ABSTRACT FROM AUTHOR]

The latest research on applying beam oscillation in laser beam fusion cutting revealed significant process improvements regarding speed and quality. The reason for this increasing process efficiency remains unexplained; however, theoretical investigations suggest the change in energy deposition (respectively heat conduction) as the cause. The present paper aims to analyze the energy deposition by a novel temperature measurement method. For this purpose, a conventional laser beam cutting setup was equipped with beam oscillation technology and a high-speed temperature measurement setup. Various characteristics of the temperature distribution in the process zone (spatial and temporal resolved temperature profiles, maximum and average values, as well as melt pool size) were evaluated for different conditions of beam oscillation (amplitude, frequency, cutting speed). Additionally, the geometrical properties of the process zone, defining the absorptivity have been measured. The comparison with static beam shaping reveals strong temperature volatility, which is induced by the way of energy deposition and an improved absorptivity over a substantial part of the cut front, with the overall result of enhanced heat conduction. For the first time, changed mechanisms applying beam oscillation instead of static beam shaping have been experimentally identified. Based on these measurements, a previously developed explanatory model was not only confirmed but also extended.

The latest research on laser beam fusion cutting (LBFC) with static beam shaping have shown a limitation in the quality of cut parts for thick steel plates (> 6 mm) when using solid state lasers. The approach of dynamic beam oscillation has recently shown to be capable of overcoming this challenge, allowing to increase the cutting speed as well as improving cut edge quality beyond the state of the art. The present paper investigates the influence of longitudinal, linear beam oscillation in LBFC of 12 mm mild and stainless steel plates by analyzing different parameters as cutting speed, burr, surface roughness, heat affected zone (HAZ), and recast layer. Reasons for the observed process improvements compared to static beam shaping have been discussed. The adjustment of the energy deposition and interaction time of the laser beam with the material found to be most relevant for optimizing the LBFC process. In particular, for beam oscillation, a gradual energy deposition takes place and increases the interaction time. This reduces the heat input in terms of HAZ and recast layer by more than 50%, resulting in high cut edge quality and more than 70% faster cutting speed.

Abstract Deformable mirrors show large potential for the dynamic beam shaping in high power laser applications. A model which is based on influence functions is used to systematically investigate the beam shaping capabilities of several deformable mirrors based on the underlying technology and the number of actuators. [ABSTRACT FROM AUTHOR]

There have been numerous efforts to use fiber-optic techniques in array antennas. Fiber-optics is attractive for the same reasons it is the technology of choice for telecommunications applications. Advantages include: a natural resistance to electromagnetic interference (EMI), low weight, small size, low intrinsic losses and the ability to easily remote components. Additionally, its unique processing capabilities permit simplifying the arrays and adding system functionality, e.g., dynamic beam shaping (adaptive beamforming) and time-steering. A wide variety of optical implementations have been proposed for time-steered array antennas. The Naval Research Laboratory (NRL) has developed a practical, fiber optic technique for implementing time-steered arrays. The approach is based upon a dispersive, fiber-optic delay line combined with a simplified beamforming architecture. This method solves many of the problems associated with optical true time delay (TTD) beamformers. It has been dubbed the fiber-optic dispersive prism. The basis for the approach is shown [ABSTRACT FROM PUBLISHER]