Abstract:Direct laser slab face-cooling by a fluid crossing the main and pump laser beams is an important method to reach high average laser powers. However, the flow regime is usually maintained at low Reynolds numbers, to prevent the onset of turbulence features in the flow, that would degrade wavefront quality. We show here how bringing the fluid temperature to the thermooptical null point, close to the water/ice transition in the case of water, allows one to mitigate the optical consequences of hydrodynamic instabi… Show more
“…Such distortions are induced by the coolant flow, as reported in Refs. [24, 25]. However, whatever the repetition rate tested, the PSD stays below the acceptable upper limit represented by the broken purple line. Figure 4 One-dimensional PSD over the (1–10 mm) range calculated from the wavefront measurements.…”
Section: Resultsmentioning
confidence: 99%
“…The amplifier cell was qualified at different repetition rates from 1 shot per few minutes to 1 shot per minute. Emphasis is herein placed on assessment of the mid-spatial-scale (1–10 mm) distortions in amplified wavefronts commonly observed in fluid-cooled amplifiers [ 25 , 26 ] . Such wavefront defects in large-aperture multi-slab laser systems are likely to degrade the focal point quality and, in the worst case, damage optical materials due to Kerr effects and/or amplitude modulation during laser beam propagation [ 17 , 27 ] .…”
Mid-spatial frequency wavefront deformation can be deleterious for the operation of high-energy laser systems. When fluid cooled high-repetition-rate amplifiers are used, the coolant flow is likely to induce such detrimental mid-spatial frequency wavefront deformations. Here, we describe the design and performance of a 90 mm × 90 mm aperture, liquidcooled Nd:phosphate split-slab laser amplifier pumped by flash-lamps. The performance of the system is evaluated in terms of wavefront aberration and gain at repetition rates down to 1 shot per minute. The results show that this single cooled split-slab system exhibits low wavefront distortions in the medium to large period range, compatible with a focus on target, and despite the use of liquid coolant traversed by both pump and amplified wavelengths. This makes it a potential candidate for applications in large high-energy laser facilities.
“…Such distortions are induced by the coolant flow, as reported in Refs. [24, 25]. However, whatever the repetition rate tested, the PSD stays below the acceptable upper limit represented by the broken purple line. Figure 4 One-dimensional PSD over the (1–10 mm) range calculated from the wavefront measurements.…”
Section: Resultsmentioning
confidence: 99%
“…The amplifier cell was qualified at different repetition rates from 1 shot per few minutes to 1 shot per minute. Emphasis is herein placed on assessment of the mid-spatial-scale (1–10 mm) distortions in amplified wavefronts commonly observed in fluid-cooled amplifiers [ 25 , 26 ] . Such wavefront defects in large-aperture multi-slab laser systems are likely to degrade the focal point quality and, in the worst case, damage optical materials due to Kerr effects and/or amplitude modulation during laser beam propagation [ 17 , 27 ] .…”
Mid-spatial frequency wavefront deformation can be deleterious for the operation of high-energy laser systems. When fluid cooled high-repetition-rate amplifiers are used, the coolant flow is likely to induce such detrimental mid-spatial frequency wavefront deformations. Here, we describe the design and performance of a 90 mm × 90 mm aperture, liquidcooled Nd:phosphate split-slab laser amplifier pumped by flash-lamps. The performance of the system is evaluated in terms of wavefront aberration and gain at repetition rates down to 1 shot per minute. The results show that this single cooled split-slab system exhibits low wavefront distortions in the medium to large period range, compatible with a focus on target, and despite the use of liquid coolant traversed by both pump and amplified wavelengths. This makes it a potential candidate for applications in large high-energy laser facilities.
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