Smoothing by Spectral Dispersion Invented

1989:

LLE scientists first pioneered smoothing by spectral dispersion (SSD) in 1989. This beam-smoothing technique is used to produce uniform beam profiles for high-power, frequency-tripled glass lasers. It paved the way for using OMEGA in direct-drive mode to explore ignition scaling of ICF capsules. 

In October 1989, “Improved Laser-Beam Uniformity Using the Angular Dispersion of Frequency-Modulated Light,” by S. Skupsky et al., was published in the Journal of Applied Physics. The article detailed the SSD beam-smoothing technique now used on all Nd:glass fusion lasers. SSD became a universal solution to the uniformity issue of a glass laser system and was subsequently adopted on all major glass laser fusion facilities, including LMJ and the NIF.

Image: The phase-plate intensity pattern in the focal plane consists of a diffraction-limited envelope upon which is superimposed a rapidly varying structure caused by the interference between rays from different phase-plate elements.

[1] S. Skupsky, R. W. Short, T. Kessler, R. S. Craxton, S. Letzring, and J. M. Soures “Improved Laser-Beam Uniformity Using the Angular Dispersion of Frequency-Modulated Light,” J. Appl. Phys. 66 (8) 3456-3462 (1989).