光折变晶体全息图的热固定特性优化的研究

Study on Characteristics of Thermal Fixing of Holograms in Photorefractive Crystals

采用红光对单、双掺铌酸锂晶体中全息光栅的热固定效率及光擦除和暗存储寿命的特性进行了深入的实验研究。实验中高掺杂和强还原晶体难以显影出离子光栅 ;对于较少掺杂的未还原晶体 ,获得离子光栅的热固定效率达 5 0 % ;高掺杂晶体中离子光栅的暗存储寿命达 4个月 ,比热固定前电子光栅的暗存储寿命提高了十几倍。实验表明热固定效率和光栅的暗存储寿命不能同时提高 ,这与理论预期一致。

The factors of affecting thermal fixing efficiency and lifetimes of fixed gratings under both illumination and dark conditions are analyzed theoretically. The characteristics of fixed reflection gratings in Fe:LiNbO3 and Ce:Fe:LiNbO3 crystals recorded using red wavelength have been extensively studied. The experimental results show that the development of ionic gratings in crystals with high concentration and deep reduction is not available. For lightly doped unreduced crystals, the thermal fixing efficiency up to 50% has been achieved. The lifetime of the ionic grating under continuous illumination is up to 300 hours, which is one hundred times more than that of the electronic grating. The dark storage time of the ionic grating for heavily doped crystals can reach 4 months, ten times more than that of the electronic grating before thermal fixing. The experimental results demonstrate that the conditions required for increasing thermal-fixing efficiency will decrease the lifetime of ionic gratings, as predicted by theory.