Editing Reflection (physics) (section)

===Complex conjugate reflection===
In this process (which is also known as phase conjugation), light bounces exactly back in the direction from which it came due to a nonlinear optical process. Not only the direction of the light is reversed, but the actual wavefronts are reversed as well. A [[phase-conjugate mirror|conjugate reflector]] can be used to remove [[Aberration in optical systems|aberrations]] from a beam by reflecting it and then passing the reflection through the aberrating optics a second time. If one were to look into a complex conjugating mirror, it would be black because only the photons which left the pupil would reach the pupil.