研究了周期性极化铌酸锂(PPLN)晶体内倍频和电光耦合的级联过程，发现引入另外一束光波，可以改变晶体内原有的三个光波的能量耦合过程。模拟结果显示，通过改变外加光波光强，可以实现对三个光波的强度和二次谐波偏振态的调制。研究结果对于同时实现倍频和信号调谐非常有益。

The cascade process of frequency doubling and electro-optic (EO) coupling in a single periodically poled niobate (PPLN) crystal is studied. The original coupling process is disturbed by the introduction of another optical wave (control light). Numerical results indicate that magnitude of three waves and the polarization of the second harmonic (SH) can be both modulated by adjusting the intensity of control light. This result would be useful when simultaneous frequency doubling and signal tuning are desired.