![]() ![]() “We don’t fully understand what type of grating aberrations are disturbing the laser beam uniformity,” says Petersson. Such timing errors can produce various unwanted effects, including a small pre-pulse of laser light that essentially “leaks” enough intensity before the main pulse arrives to compromise the experiment. The code will give scientists for the first time a powerful simulation tool to predict the performance of a realistic laser compressor.ĭespite advanced manufacturing techniques utilized by Livermore and industry, gratings may possess minute imperfections that can result in imperfect diffraction, which in turn yields an imperfect alignment of all wavelengths in time. Their code is called GEFIE-QUAD for gratings electric field integral equation on quadrilateral grids. The team is developing a first-principles simulation method to model the interaction of laser light with diffraction gratings, and to determine how grating imperfections can affect the performance of the compressor in a CPA laser system. With Laboratory Directed Research and Development funding, a team of Computing scientists, led by Anders Petersson and joined by National Ignition Facility postdoctoral researcher Sam Schrauth, is advancing that simulation expertise. Livermore’s dominance in the growing field of high-energy, short-pulse lasers will be further aided by Computing’s capability to simulate the physical processes of lasers and their interaction with matter. By careful geometric arrangement of the four gratings, different frequencies of laser light can be made to travel different distances through the device, thus modifying the duration of a laser pulse. Both the stretcher and compressor normally consist of four diffraction gratings. The reflection angle depends on the wavelength and the spacing between the very fine lines inscribed in the grating’s metallic substrate (typical spacing is approximately 1 micrometer). In the final stage of the CPA laser, the pulse is compressed in time by a set of diffraction gratings, in which the shorter wavelengths “catch up” with the longer wavelengths to achieve a cohesive, short-duration, very-high-intensity laser pulse that is focused on a target.Ī diffraction grating is an optical component that separates incoming light into its constituent wavelengths. After this step, shorter (blue) wavelengths of higher frequencies lag behind the longer (red) wavelengths of lower frequencies of the light pulse. Length scales range from the wavelength and line spacing of about 1 micrometer to the laser beam diameter (d) of about 0.1 meter.ĬPA laser systems first stretch out in time a short pulse of low-intensity light, converting it into a lower-intensity, longer-duration (thousands of times longer) pulse that can be amplified without damaging costly laser optics. The large range of length scales makes chirped pulse amplification simulations computationally challenging. ![]()
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