Abstract
A novel technique of measuring the prompt, thermally induced wave-front aberrations in a large aperture flash-lamp pumped Nd3+ glass disk amplifier is presented. Implementing a 2 × 2 lens array and a 2 × 2 position sensitive detector array as a diagnostic system, the wave-front profile was successfully reconstructed for the first five Zernike terms for a temporal window of 8.5 ms.
Highlights
Petawatt class Nd:glass laser facilities, such as the Vulcan laser system at the Central Laser Facility (CLF, RAL), often rely on large aperture flash-lamp pumped disk amplifiers to generate high energy laser pulses
The thermal loading in the disks lead to thermally aberrated laser beams reducing the focal spot intensity needed for high intensity experiments
The results presented in this paper are based on a large aperture disk amplifier, which consists of six Nd:glass disks pumped by two sets of four flash-lamps
Summary
Petawatt class Nd:glass laser facilities, such as the Vulcan laser system at the Central Laser Facility (CLF, RAL), often rely on large aperture flash-lamp pumped disk amplifiers to generate high energy laser pulses. Flash-lamps, as pumping sources, offer many advantages; their broad spectrum is suitable when pumping large Nd:glass disks with five separate pump bands and they are an inexpensive method of providing high pump energy.. The thermal loading in the disks lead to thermally aberrated laser beams reducing the focal spot intensity needed for high intensity experiments. A laser beam propagating through a medium with a temperature gradient will experience a nonuniform change in the optical path length, which results in an aberrated beam. This study will define an efficiency factor χa, which takes into account the focal beam quality due to the thermal loading (Strehl ratio) and the small signal gain in the amplifier. The temperature gradient results in the optical path length of the beam changing nonuniformly, which is why an efficiency factor taking into account the rms wave-front error is more meaningful
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