Improvement of irradiation uniformity by dynamic interference structures of laser array in inertial-confinement-fusion facilities

Abstract

In order to improve the irradiation uniformity in inertial confinement fusion facilities, a novel scheme, smoothing by interference structures of laser array, is firstly proposed for improving the irradiation characteristics. In this approach, a pair of identical phase plates with either tilted, cylindrical, elliptical or spiral phase modulates two beamlets, and another pair of phase plates that are conjugate with the former reshapes another two beamlets. Between the beamlets with conjugate wavefront distributions, their central wavelengths are shifted but their polarization states are the same. Arising from the combined effect of the conjugate wavefront distributions and the wavelength differences among the beamlets, the dynamic interference structures are generated in the focal region and thus improve the irradiation uniformity of these beams. Simulation shows that, the superposed focal spot of the beamlets in the focal region is smoothed in transverse, radial or azimuthal direction due to the phase types of the plates, and the required time to achieve the best uniformity is much shorter than the smoothing by spectral dispersion scheme. Moreover, the phase plates can be integrated with the continuous phase plates or be placed in the beamline as pure phase plates in the high-power laser facilities.