KNbO3:Fe晶体的最佳二波耦合

本文在分析光折变晶体KNbO3:Fe的最佳二波耦合条件的基础上,通过计算和实验研究了晶体KNbO3:Fe的二波耦合增益系数Γ与两光束的夹角2θ、光栅矢量的取向β及不同电光系数r51或r42的关系,获得了在特定掺杂浓度N～1016cm-3条件下KNbO3:Fe晶体的最佳二波耦合条件为:θm～4°-8°并且βm～45°.

OPTIMAL TWO-WAVE COUPLING IN KNbO3:Fe CRYSTAL

In this paper two-wave coupling in photorefractive KNbO3:Fe crystal is discussed in order to obtain the optimal conditions, under which the two-wave coupling exponential gain r reaches the maximum point.KNbO3:Fe crystal is an important photorefractive material.Its advantages are the fast response time and high sensitivity. The exponential gain r depends both on material propertiess,such as electro-optical tensor components rij and concentration of traps N, and on externally controlled parameters,such as the angle between the two incident beams inside the crystal 2θ, the angle between the grating vector and the crystal optical axis β,etc. We have studied two KNbO3:Fe crystal specimens with N1=1.8×1016cm-8and N2= 1.1×1016cm-3 respectively. And one of them (the second one) is specially cut so that we can obtain β-value near 45° for small 2θvalue.