We demonstrate ultrafast high-power laser operation, both at multi-kW average power in ultrashort-pulsed operation over extended bursts with hundreds of MHz intra-burst repetition rate from a modified TruMicro 6020 industrial laser, as well as uninterrupted, quasi-CW operation at an average power beyond 1 kW obtained with a TEM00 multipass thin-disk laser booster amplifier. The pulse repetition rate can be varied from 50 MHz to beyond 1 GHz, with single-pulse energies well above 10 μJ and single-pulse peak powers far beyond 10 MW without a post-compressor. These systems are attractive, e.g., for high-throughput materials processing or for driving nonlinear processes.
The increasing use of short – and ultrashort pulsed lasers in industrial applications leads to a demand for high power industrial-grade lasers covering a large range of pulsed laser parameters. We will present a comprehensive overview of our latest pulsed laser results based on different laser building blocks such as seed lasers, fiber amplifiers, rod and slab amplifiers, thin disk amplifiers and combinations thereof. Along with the technical insights we will give an outlook on the next development steps to further scale these parameters.
Driving nonlinear processes in scientific and upcoming industrial applications has been a topic with increasing interest and activities in the last years. Examples are the production of very short wavelengths via direct driven plasma light-sources (incoherent) or high-harmonic generation (coherent), optical parametric chirped pulse amplification to different wavelengths and shorter pulses and direct pulse shortening via self-phase modulation and subsequent compression down to the few-cycle pulse duration regime. We report on multi100W ultrafast laser sources with 1ps pulse durations and below and <10mJ pulse energies based on the InnoSlab laser-concept. Achieved beam qualities are M2<1.2 at average power stabilities in the 0.1% regime. Measured pulse stabilities are around 1% (rms) and pulse intensity contrasts well exceed 50dB for preceding or following pulses. These stability values together with the high average pulse power are very well suited for use as drivers of nonlinear optical processes. We show that these sources can be integrated into very compact housings with full computer control which additionally eases the practical use for further processing of the radiation.
Industrial ultrafast lasers such as TRUMPF’s TruMicro Series are indispensable tools in many precision machining processes. Large 24/7 applications range from machining of sapphire or glass to ceramics, polymers, and metals in industries from the automotive sector to consumer electronics. In typical installations such pico- and femtosecond lasers currently operate at average power levels up to 150 W, often with nonlinear frequency conversion to the visible or UV. Based on the advanced amplifier technology pioneered by AMPHOS we introduce our new hybrid fiber–InnoSlab amplifier generation TruMicro Series 6000, capable of producing the highest average power at utmost flexibility and reliability.
Ultrafast lasers are the ideal tool for a wide range of applications in materials processing. Especially the modification of surfaces of any kind of material like glass, metal and plastics will have huge impact on many high-tech products. Surface structuring is used to generate specific surface properties and as the processes are different and a wide variety of scanning solutions form Galvo with diffractive elements up to polygonscanners are used to distribute the energy onto the surface, the ideal laser source allows to address a broad parameter range. InnoSlab amplification technology is the ideal candidate for that as it is shown in this paper.
We demonstrate a femtosecond Yb:YAG InnoSlab laser amplifier producing <3mJ pulse energy at 100kHz pulse repetition rate. The minimal pulse duration is <1ps resulting in pulse powers <3GW. High energy and high average power could be obtained with the use of chirped pulse amplification on the power amplifier end. The laser setup consists of a seed laser with 10mW average power at pulse repetition rates of 100kHz to 1MHz, a pre-amplifier stage, a highpower InnoSlab-amplifier stage and a grating based pulse compressor. This laser source is suited for pumping of OPCPA setups und parallelisation of applications in materials processing.
We demonstrate a femtosecond Yb:YAG InnoSlab laser amplifier producing 450-μJ pulse energy at 500kHz pulse repetition rate. Ultrafast operation at high energy and high average power could be obtained without the use of chirped pulse amplification on the power amplifier end. The laser setup consists of a compact and robust femtosecond fiber based seed laser producing up to 4μJ pulses with pulse durations down to 260fs. Pulses from the seed source are directly amplified to high pulse energy and average power in an optimized Innoslab amplifier. This laser source is ideally suited for large scale industrial applications requiring high average power ultrashort pulses for high throughput and productivity.
We report on the development and experimental analysis of an LED lighting module for use in a high-end food lighting
environment which puts high demands on color homogeneity and color rendering. The system is built from highly
reflecting and partly scattering PVD coated metal reflector sheet that has limited deformability and uses RGBW LEDs.
We develop an optical design that is adapted to allow for color mixing and to take into account manufacturing
constraints and include this into a prototypical module. Results of measurements and field tests are in good agreement
with simulations.
A flexible ultrafast laser amplifier system based on Ytterbium Innoslab technology with an average power exceeding
200W is presented. The pulse duration of the system can be continuously tuned between 500fs and 6ps, limited only by
the amplification bandwidth of Yb:YAG and the stretcher of the seed source. The repetition rate can be varied from
26.6MHz down to 1MHz. For the ps-regime more than 200μJ and for the fs-regime more than 50μJ are demonstrated
without the need of temporal compression of the high power beam after the amplifier. Spectral bandwidth is close to the
transform limit of the shortest measured pulses. Beam quality is measured to be near the diffraction limit (M2<1.3).
KEYWORDS: Light emitting diodes, Lenses, Ray tracing, Light sources and illumination, Polymers, Lens design, Monte Carlo methods, LED lighting, Freeform optics, LED displays
We report on the development and experimental analysis of novel freeform polymer lenses for the uniform illumination
of a target area using high-brightness LED. In a first step, the LED module was centered over the illuminated area and
the two faces of a freeform lens were designed for homogeneous and efficient light distribution. In a second step, the
system was extended for an off-axis target, the overall size was reduced and structures for automated alignment with
respect to the LED were included. Photometric analyses were used for each system and were found to be in good
agreement with simulations.
Recent progress in rare-earth doped fibers has allowed Yb-doped fiber lasers to be power-scaled to several kW's.
Remarkably, the continued rise of the fiber laser output power into multi-kW range is being limited by the pump diodes
rather than the fibers themselves.
In this article we discuss our recent progress in the development of high-brightness fiber-coupled laser diode modules for
pumping Yb and Er doped lasers. Pumps based on laser diode arrays as well as on multiple single emitter platforms will
be described. The prospects of power scaling as well as expected limitations to different designs will be discussed.
We demonstrate 976 nm pump module with 55W ex-fiber output power from 105 μm core diameter fiber. The coupling
efficiency was 58%. Similar approach was used for realization of 1450 nm diodes and as a result over 15 W CW power
was achieved from the fiber with the same aperture.
Volume holographic gratings (VHG) provide the capability of narrowing and stabilizing the wavelength of
semiconductor lasers by forming an external cavity laser (ECL). The standard configuration of these ECL's is to use a
collimating lens followed by the VHG to provide feedback to the resonator and lock the wavelength. In this
configuration both elements have to be carefully aligned with tolerances in the sub-µm and mrad range. The present
paper presents a fast-axis collimation lens (FAC) with integrated VHG for locking a laser diode bar. Besides the
advantage of having only a single element, the integrated element is also less sensitive to alignment tolerances with
respect to the locking due to the large divergence angle of the uncollimated array compared to a collimated array. Using
a standard AR coated array with 19 emitters an output power of 67.4 W was achieved. The spectral bandwidth was
within 1 nm over the whole power range. Due to high stability requirements in this application, glass was chosen as the
VHG material. Though the refractive index is low compared to standard FAC lenses, the design and manufacturing
process of the lens still guarantees a diffraction limited collimated beam.
The materials processing industry has recently mandated the need for more efficient laser systems with higher beam quality and longer life. Current multiplexing techniques, state-of-the-art laser diodes and novel cooling designs are now emerging as possibilities to meet the ever demanding industry needs. This paper describes the design and initial results of a direct diode system that is aimed at delivering 1.5 kW of output power and a beam divergence of 40 mm mrad on a long life macro-channel cooler. The design entails multiplexing 2 wavelength combined beams and 2 polarization combined beams. Each of the four branches of the direct diode system utilizes a novel stacking and cooling design. The results from one of these branches, 1 wavelength and 1 polarization, are presented where the light is coupled into a fiber with a 400 μm core diameter and a NA of 0.22. Each branch consists of 60 diode laser mini-arrays, where each mini-array consists of four 100 μm wide emitters and a lateral fill factor of 50%. An output power of 500W at 10°C water temperature and 420 W at 25°C are demonstrated through the 400 μm fiber.
High power diode pumped solid state lasers are auspicious sources for various applications in material processing. The solid state laser we report on is a Nd:YAG slab laser, that is partially end pumped from two ends by the line focus of two diode laser stacks. The pumped volume has a rectangular cross section. The resonator is configured, so that it is stable in the plane of small dimension and off axis unstable in the plane of large dimension of the gain cross section. Unlike conventional slab laser design, in which the laser beam takes zick zack path inside the slab crystal, in the present design the beam goes straight through the crystal with perpendicular end faces.
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