Suppression of FM-to-AM conversion in third-harmonic generation at the   retracing point of a crystal
  FM-to-AM conversion can cause many negative effects (e.g., reducing of margin against damage to the optics, and etc.) on performances of third-harmonic conversion system. In this letter, the FM-to-AM conversion effect in third-harmonic generation is investigated both at and away from the retracing point of type-II KDP crystal. Obtained results indicate that the FM-to-AM conversion can be suppressed effectively when the crystal works at the retracing point. 
Yisheng Yang, Bin Feng, Wei Han, Wanguo Zheng, Fuquan Li, and Jichun   Tan
physics.optics