In this paper, we show results of further brightness improvement and power-scaling enabled by both the rise in chip brightness/power and the increase in number of chips coupled into a given numerical aperture. We report a new chip technology using new extra Reduced-mode (x-REM) diode design providing a record ~363 W output from a 2×12 nLIGHT element® in 105 μm diameter fiber. There is also an increasing demand for low size, weight and power-consumption (SWaP) fiber-coupled diodes for compact High Energy Laser (HEL) systems for defense and industrial applications. Using thirty single emitters that were geometricallyand polarization-combined, we have demonstrated 600 watts and 62% efficiency at in 225 μm/0.22 NA fiber resulting in specific mass and volume of 0.44 kg/kW and of 0.5 cm3/W respectively. Furthermore, we have increased the number of chips to forty and increased the output power to 1kW and 52% in the same fiber diameter and numerical aperture. This results in a fiber-coupled package with specific mass and volume of <0.18 kg/kW and <0.27 cm3/W, respectively.
We demonstrate a robust, compact, low-cost, pulsed, linearly polarized, 1064 nm, Yb:fiber laser system capable of generating ~100 kW peak power pulses and >17 W average power at repetition rates of 80 – 285 kHz. The system employs a configurable microchip seed laser that provides nanosecond (~1.0 – 1.5 ns) pulse durations. The seed pulses are amplified in an all-fiber, polarization maintaining, large mode area (LMA) fiber amplifier optimized for high peak power operation. The LMA Yb:fiber amplifier enables near diffraction limited beam quality at 100 kW peak power. The seed laser, fiber amplifier, and beam delivery optics are packaged into an air-cooled laser head of 152×330×87 mm3 with pump power provided from a separate air-cooled laser controller. Due to the high peak power, high beam quality, spectral purity, and linearly polarized nature of the output beam, the laser is readily frequency doubled to 532 nm. Average 532 nm powers up to 7 W and peak powers exceeding 40 kW have been demonstrated. Potential for scaling to higher peak and average powers in both the green and infrared (IR) will be discussed. This laser system has been field tested and demonstrated in numerous materials processing applications in both the IR and green, including scribing and marking. We discuss recent results that demonstrate success in processing a diverse array of representative industrial samples.
We report on the performance of a 100 W, 105μm, 0.17 NA (filled) fiber-coupled module operating at 976 nm. Volume
holographic (Bragg) gratings are used to stabilize the emission spectrum to a 0.2 nm linewidth and wavelengthtemperature
coefficient below 0.01nm/°C with virtually no penalty to the operating power or efficiency of the device.
The typical fiber coupling efficiency for this design is >90%, enabling a rated operating efficiency of ~50%, the highest
reported for a 100W/105μm-class diode pump module (wavelength stabilized or otherwise).
Diode laser modules based on arrays of single emitters offer a number of advantages over bar-based solutions including
enhanced reliability, higher brightness, and lower cost per bright watt. This approach has enabled a rapid proliferation of
commercially available high-brightness fiber-coupled diode laser modules. Incorporating ever-greater numbers of
emitters within a single module offers a direct path for power scaling while simultaneously maintaining high brightness
and minimizing overall cost. While reports of long lifetimes for single emitter diode laser technology are widespread, the
complex relationship between the standalone chip reliability and package-induced failure modes, as well as the impact of
built-in redundancy offered by multiple emitters, are not often discussed. In this work, we present our approach to the
modeling of fiber-coupled laser systems based on single-emitter laser diodes.
We present the latest development of high brightness, diode laser systems at Coherent Direct Diode Systems.
Experimental results on diode laser modules with greater than 100 W with beam quality better than 10 mm•mrad
will be presented. Through a combination of diode laser emitter improvements and narrow-band (< 10 nm)
wavelength combination, we improve the spatial beam quality of diode laser systems significantly. The presentation
will show a path that scales these diode laser systems to a kW-class output power from a 100 μm fiber with a single
wavelength.
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