Dynamic properties of multiple grating formation in doped and thermally treated lead germanate

During holographic recording: in lead germanate (Pb5Ge3O11) crystals two ty pes of refractive-index gratings are observed. One has a very fast response whereas the second builds up comparably slowly. Measurements of diffractio n efficiency and two-beam coupling are carried out to study the formation o f both gratings and to obtain the relative phase between them. Differently doped and thermally treated samples are divided into four classes due to th eir different time evolution of diffraction efficiency and of the energy tr ansfer direction during two-beam coupling. The classification depends on do ping and treatment. For Ni-doped and thermally treated samples dark and pho to conductivities corresponding to the slow grating are determined, indicat ing that Ni-doping combined with oxidation enhances the properties of the s low grating.