利用掺杂KNSBN晶体，报道了两束异常偏振光所引起的各向异性锥形衍射现象。首次观察到一种由三个衍射光锥所组成的各向异性衍射图样，并且提出了由入射光和满足相位匹配条件的前向散射光所参与的光折变四波混频机制。对双光束对称入射这种特殊实验配置情形，给出了衍射光锥的锥角随入射角的变化关系式，理论分析和实验结果符合得很好。

The anisotropic conical diffraction generated by two extraordinary polarized beams with doped KNSBN crystals is reported. An anisotropic diffraction pattern with three diffraction cones has been observed for the first time. And the mechanism of photorefractive four wave mixing involved the incident beams and forward scattered beams satisfying the phase matching condition is proposed. For the experimental geometry in which the two beams incident on the sample symmetrically, we presented the dependence of the diffraction cones on the incident angles. The theoretical analysis agrees well with the experimental results.