光折变晶体两波耦合增益系数强度特性理论研究

对两中心模型光折变晶体两波耦合增益系数Γ,总的有效陷阱密度N_eff和强度特性因子η(I)的强度特性进行了理论研究。结果显示在两中心模型的光折变晶体中,Γ,N_eff和η(I)有着复杂的特性。当S_Dγ_T/S_Tγ_D小时,对于A类和B类两中心晶体,N_eff随强度的增加而增加最终趋于饱和,当S_Dγ_T/S_Tγ_D大时,对于A类晶体N_eff增加到一个最大值后稍有减少,而对于B类晶体,N_eff增加到最大值后然而有较大的减少。不同类型晶体增益系数Γ有着不同的强度特性是由于晶体中有着不同的能级结构。

Theoretical study of the intensity dependence of two-beam coupling gain coefficient in photorefractive crystals

Intensity dependence of the two-beam coupling gain coefficient Γ, the effective trap density Neff and the intensity dependent fact or η(I) is studied theoretically for the two-centre photorefractive crystals. The results show that Neff, η(I) and Γ have more co mplicated behaviors in two-centre crystals. When SDγT/STγD is small, Neff increases and tends to saturate with increasi ng intensity for both type-A and type-B two-centre crystals. W hen SDγT/STγD is large, Neff increases to a maximum and then decreases a little for type-A crystals and decreases greatly for type-B crystals.The different intensity dependence of Γ in the two types of crystals comes from their different level structures.