Progress in joule-class diode laser bars and high brightness modules for application in long-pulse pumping of solid state amplifiers

Crump, P.; Karow, M. M.; Knigge, S.; Maaßdorf, A.; Tränkle, G.; Lotz, J.; Faßbender, Wilhelm; Neukum, J.; Körner, Jörg; Bödefeld, R.; Hein, Joachim

doi:10.1117/12.2252246

Cited by 1 publication

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“…Overall, commercially available pump sources partly fulfil the EuPRAXIA requirements. Some achieve the requested brightness of >1 MW/cm 2 /sr [2,5,7,9,13] others fulfil the required f = 20 Hz to 100 Hz [7,9]. Full performance is only achieved when microchannel coolers are allowed.…”

Section: Introductionmentioning

confidence: 99%

Novel High-Power, High Repetition Rate Laser Diode Pump Modules Suitable for High-Energy Class Laser Facilities

et al. 2019

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The latest generation of high-energy-class pulsed laser facilities, under construction or planned, such as EuPRAXIA, require reliable pump sources with high power (many kW), brightness (>1 MW/cm2/sr) and electro-optical conversion efficiency (>50%). These new facilities will be operated at high repetition rates (around 100 Hz) and only diode lasers are capable of delivering the necessary performance. Commercial (quasi-continuous wave, QCW) diode laser pulse-pump sources are, however, constructed as low-cost passively cooled stacked arrays that are limited either in brightness, efficiency or repetition rate. Commercial continuous wave diode laser pumps constructed using microchannel coolers (as used in high-value industrial machine tools) can fulfil all requirements, but are typically not preferred, due to their cost and complexity and the challenges of preventing cooler degradation. A custom solution is shown here to fill this gap, using advanced diode lasers in a novel passive side-cooling geometry to realize 100 … 200 Hz pump modules (10%–20% duty cycle) that emit peak power of 6 kW at wavelength = 940 nm. The latest performance of these modules is summarized and compared to literature. We show that a brightness >1 MW/cm2/sr can be efficiently delivered across a wide range of laser pulse conditions with 10% duty cycle (pulse width: 100 µs … 100 ms … cw, repetition rate up to 1 kHz). Furthermore, we describe how these pumps have been used to construct and reliably operate (>109 pulses without degradation) in high-energy-class regenerative and ring amplifiers at the Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI). We also show first results on 100 Hz pumping of cryogenically cooled solid-state Yb:YAG slab amplifiers, as anticipated for use in the EuPRAXIA laser, and note that peak temperature is disproportionately increased, indicating that improved cooling and more detailed studies are needed.

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