[OPTICAL REVIEW Vol. 5, No. 5 (1998) 285-290]
Improvement of Laser-Beam Irradiation-Intensity Distribution Using Multi Lens Array and Edge-Shaped Plates
Noriaki NISHI,* Takahisa JITSUNO, Masahiro NAKATSUKA and Sadao NAKAI
Institute of Laser Engineering, Osaka University, 2-6, Yamada-oka, Suita, Osaka, 565-0871 Japan
(Received November 17, 1997; Accepted May 21, 1998)
A new concept for improving the laser intensity distribution on an inertial confinement fusion target using a phase-controlled multi lens array has been proposed. Circular and hexagonal element lens apertures have been examined, and the circular aperture which eliminated azimuthally asymmetric intensity distribution was chosen. The diffraction fringe of the elementary lens was mitigated in a one-dimensional lens array using edge-shaped plates of a super-Gaussian phase profile. Uniform beam profiles were obtained using a one-dimensional array with 7 spherical lenses and a two-dimensional array with 37 lenses. An approximately flat-top intensity distribution was realized with the lens array with 37 lenses.
Key words : envelope profile control, illumination uniformity, multi lens array, diffraction fringe, edge-shaped plate