Concentration of light by inverting its wavefront
Pilipetskii M.F., Popovichev V.I., Ragul'skii V.V.
The principle of automatic focusing of light on a target is realized. A flat target of small diameter was illuminated with a ruby laser. The light from the target was amplified and then subjected to stimulated scattering with inversion of the wavefront. The scattered radiation, going through the amplifier in the backward direction, was practically entirely incident on the illuminated region, regardless of its position in space and regardless of the presence of aberrations in the optical elements.