We have designed a square-shaped beam homogenizer using a lens array for pumping a petawatt-class Ti:sapphire amplifier. The designed beam homogenizer generated a flat-top uniform square pump beam with 5.1% of edge steepness and 2.7% of RMS spatial uniformity, respectively. This pump beam generated an output beam with 74 J of energy and 56.8% of extraction efficiency, respectively. A scalar diffraction and two-dimensional amplification simulation were performed for optimization. The results indicate the possibility of improving an amplification efficiency and developing a compact square petawatt-class laser system.

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We mathematically model the thermal lens effect of Ti:sapphire for use in a high-power laser pulse amplifier. The model enables more accurate prediction with new interpretations and offers simplified equations for the optical path difference and thermally induced focal length. Our model is validated through comparisons with measurements of existing high-power laser facilities. Further, we apply the model to a 2 PW, 10 Hz Ti:sapphire laser amplifier design.

Abstract. We proposed a zoom homogenizer that can control the size of the illumination field by adding one lens array to the conventional imaging-type beam homogenizer. An equivalent lens system was used to derive the imaging condition and size of the illumination field. The result of the ray-tracing simulation shows the validity of the zoom homogenizer to generate the uniform and sharp-edged beam. We presented the strengths and weaknesses of the zoom homogenizer in terms of its etendue with the maximum acceptance angle of the system. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

We propose the insertion of a saturable absorber (SA) in a nanosecond double-pass laser amplifier as an amplified spontaneous emission (ASE) suppressor. To analyze the influence of the SA, a theoretical model is developed. One-dimensional simulation results show reasonable agreement with measurements in terms of the output energy and temporal pulse shape. For our amplifier parameters, when an SA of initial transmission 0.5 is inserted, the simulation anticipates the ASE to be reduced by a factor of 0.37 while the output pulse energy is maintained.