The refractive index of optical materials can be modified by means of neutron irradiation. By varying the radiation dose over selected areas of a lens according to some given law, the local change in the refractive index can be adjusted to correct for different types of optical aberrations. The particular case of spherical aberration is treated in detail. It is shown that irradiation leads to index modifications of the required order of magnitude and that irradiation times are acceptable. Moreover, the stability of the index modifications, the possibility of bleaching—without curing the index—and the absence of residual radioactivity make an irradiated lens suitable for optical applications. The optician has thus at his disposal a new parameter.
P. Sinai, "Correction of Optical Aberrations by Neutron Irradiation," Appl. Opt. 10, 99-104 (1971)