8 December 1997 Large-aperture kinoform phase plates in fused silica for spatial beam smoothing on Nova and the Beamlet lasers
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Proceedings Volume 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference; (1997) https://doi.org/10.1117/12.294314
Event: Second International Conference on Solid State Lasers for Application to ICF, 1996, Paris, France
Abstract
It is now widely recognized that spatial beam smoothing (homogenization) is essential in coupling the laser energy to the inertial confinement fusion (ICF) targets'. For the indirect drive approach' to ICF, it is desirable to distribute the laser energy into a uniformly speckled profile that has a flat-top super-Gaussian envelope (8th power or higher) and contains greater than 95% of the energy inside the super-Gaussian profile. Spatial smoothing is easily achieved by introducing a binary random phase plate (RPP) in the beam. This produces a homogenized far-field pattern which consists of an overall envelope function determined by the RPP element superimposed with a fine scale speckle pattern arising due to the interference among the various RPP elements. Although easy to fabricate and currently in routine use in many fusion laboratories2, the binary RPPs do not meet the ICF requirements stated above since the far-field intensity profile is restricted to essentially an Airy function containing only 84% (an upper limit) of the energy inside the central spot. Approaches using lenslet arrays (refractive or diffractive)3'4 have limited use since they operate in the quasi-far-field and have a short depth of focus.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael C. Rushford, Sham N. Dixit, Ian M. Thomas, A. M. Martin, Michael D. Perry, "Large-aperture kinoform phase plates in fused silica for spatial beam smoothing on Nova and the Beamlet lasers", Proc. SPIE 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference, (8 December 1997); doi: 10.1117/12.294314; https://doi.org/10.1117/12.294314
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