Smoothing of focused-beam pattern using two-dimensional spectral dispersion performed at GEKKO XII

Noriaki Miyanaga; Shinichi Matsuoka; Jin-Hun Park; Kouji Tsubakimoto; Masahiro Nakatsuka; Akihiro Morimoto; Tetsuro Kobayashi

doi:10.1117/12.294252

8 December 1997 Smoothing of focused-beam pattern using two-dimensional spectral dispersion performed at GEKKO XII

Noriaki Miyanaga, Shinichi Matsuoka, Jin-Hun Park, Kouji Tsubakimoto, Masahiro Nakatsuka, Akihiro Morimoto, Tetsuro Kobayashi

Author Affiliations +

Proceedings Volume 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference; (1997) https://doi.org/10.1117/12.294252
Event: Second International Conference on Solid State Lasers for Application to ICF, 1996, Paris, France

Abstract

The laser irradiation uniformity on the target surface has been improved using a 2D scheme of the smoothing by spectral dispersion. The laser beam was dispersed in both orthogonal directions by installing the series of pair of phase modulator and diffraction gratings. A polarization- preserving single mode fiber was utilized as the first phase modulator by which the modulation frequency and depth are easily controlled by using the cross-phase modulation. The second phase modulator was a quasi-velocity matched LiTaO₃ modulator driven by 9.4-GHz microwave. Using these modulators, the combination of modulation frequencies was varied in a range from 5/9.4 GHz to 14/9.4 GHz. The advanced phase modulation was obtained by adopting the self-phase modulation in conjunction with the cross-phase modulation in the optical fiber. It has been confirmed that the temporally changing modulation frequency (the chirped phase modulation) is favorable for better smoothing in comparison with the ordinary scheme with fixed modulation frequencies.

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Noriaki Miyanaga, Shinichi Matsuoka, Jin-Hun Park, Kouji Tsubakimoto, Masahiro Nakatsuka, Akihiro Morimoto, and Tetsuro Kobayashi "Smoothing of focused-beam pattern using two-dimensional spectral dispersion performed at GEKKO XII", Proc. SPIE 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference, (8 December 1997); https://doi.org/10.1117/12.294252

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