Progress is presented on ongoing research and development into ultra-high power and efficiency bars that achieve significantly higher useful optical output power and higher brightness than are currently commercially available. In previous work (2017), the authors reported on bars that deliver over 1 kW continuous wave (cw) diode laser power, when cooled using 15°C water. Our current studies are focused on increasing the usable output power (power within a targeted beam angle), which is essential for real world industrial applications. These ongoing studies have enabled the first demonstration of 500 W cw output power from a 10 mm x 6 mm laser diode bar with a lateral far field angle of only 8°. In efforts to further improve brightness, we also present our latest progress on high power SMEBs (Single Mode Emitter Bars). These emitters operate in a close to diffraction limited optical mode (M² < 1.5, laterally and vertically). This new technology enables a significant increase in Diode Laser brightness. We demonstrate in excess of 55% electro optical efficiency at > 200 W cw laser bar power for SMEBs.
We present the nearly diffraction-limited propagation of 800 W of cw laser power through 100 m of delivery fiber
having a core diameter of 30 μm. The laser source was a single-mode MOPA consisting of a fiber oscillator and two
amplifier stages and was matched to the delivery fiber through a 500 mm long taper. At a maximum power of 800 W, a
M<sup>2</sup> value of 1.35 was measured after 100 m of passive fiber. A minor Stokes-shifted spectral content was observed above
A passive few-mode multicore fiber consisting of 7 coupled cores is investigated. The fiber is compared to a largemode-
area step-index fiber, with the same number of modes and a similar mode field area. Based on the 7-core
fiber results a single transverse mode multicore fiber, with a mode field area of 465 μm<sup>2</sup> at 1050 nm, delivering
virtually diffraction limited output beam quality is demonstrated. Stimulated Raman threshold measurements
are presented and a fundamental mode high-power beam transport with more than 350 W is shown.
The objective of the present work is to develop a fiber suitable for high-power fundamental-mode beam delivery over a
useful length for material processing (~100 m). The investigated design is based on evanescent-field coupled
waveguides, also called multi-core fibers (MCFs) -. The investigated MCF consists of a hexagonal array of 7 cores
in which the fundamental mode, the so-called in-phase supermode, has an effective mode area (A<sub>eff</sub>) of 348 μm<sup>2</sup> and a
numerical aperture (N.A.) of 0.035.
We show how the bending-induced losses and the mode-mixing depend on the bending radius and on the structure of the
waveguide. The experimental results on the behavior of the near-field and the far-field for different bending radii will
also be reported. Additionally, we will show another method to reproduce experimental results with multi-mode fibers
supporting few modes where the conventional approach leads to irreproducible results due to the mode-mixing effect.