Grating spacing dependence of nonvolatile photorefractive holographic recording in doubly doped LiNbO_3 crystals

摘要

Grating spacing has great influence on grating formation via electron transport in the conduction band during holographic recording. Grating spacing dependence of two center holographic recording is investigated by writing nonvolatile holograms in doubly doped LiNbO_3 crystals. Several types of electron characteristic transport lengths are defined. The effects of electron characteristic transport lengths and oxidation-reduction state on the amplitude of nonvolatile holographic grating are numerically discussed within the range of grating spacing from 0.14μm to 10μm. It is found that the bulk photovoltaic effect is the dominant electron transport mechanism of doubly doped LiNbO3 crystals, while the diffusion effect does have appreciable effect on the grating formation when grating spacing is smaller than 1μm. Theoretical analysis and experimental results confirm that the logarithm of the amplitude of nonvolatile holographic grating Log (δn) increases with increasing grating spacing Λ within region of small grating spacing (Λsmaller than 1μm) and further increasing of grating spacing won's influence the values of Log (δn) greatly.