给出了在周期性极化铌酸锂晶体中同时包含声光调制和倍频产生的耦合波方程。声波既可以通过外部的换能器馈入，又可以通过在y方向加上交流电场而在铌酸锂晶体内部直接激发。周期性极化铌酸锂的周期倒格矢用于补偿倍频的波矢失配量，而合适频率的声子则通过光子散射来改变抽运光的偏振态。模拟结果显示，在相位匹配的条件下声光偏振耦合与倍频直接存在着竞争效应。三个光波的强度或者偏振态可以通过声光作用得到有效的调制。

Wave-coupling equations including acousto-optical (AO) polarization rotation and frequency doubling in periodically poled lithium niobate (PPLN) are proposed. The acoustic wave could either be induced from an external transducer or self-generated in PPLN driven with a cross-field radio frequency field. The proper reciprocal of PPLN is used to compensate the second harmonic generation (SHG) wave-vector mismatching, while phonon with suitable frequency may affect the pump polarization by scattering photons. Numerical simulation shows that there is a competition between the AO polarization rotation and SHG in PPLN under the phase-matching condition. The influences of the acoustic wave intensity on the polarization or intensity of three waves are studied.