Neutron diffraction — photorefractive materials enter a new research and application branch

Light-induced changes of the refractive index are referred to as photorefractive effect. Thereby it does not matter whether the light causing and the light sensing these changes have different wavelengths—from the infrared to the 7-ray spectral region— or not. In this paper we intend to generalize the notion of a photorefractive effect to cover also light-induced changes of the refractive index for neutron waves (photorefractive effect of a second kind). The scope of possible applications of photorefractive materials is extended towards holographic optical elements for neutron optics.