本文给出了串接倍频的原理及两块晶体相对取向的要求.利用两块1.4cm厚的Ⅱ类KDP晶体串接,入射基频激光强度为0.33～0.67GW/cm~2,外转换效率达到60%以上,激光束口径为φ42mm.实验结果与计算值符合很好.本文将L_1=L_2=1.4cm的串接倍频器与厚度分别为3cm和1.4cm的单块晶体倍频器的实验特性作了比较,表明串接倍频器同时兼有单块厚晶体倍频器和单块薄晶体倍频器的优点.

The theory of tandem SHG and the requirement on the relative orientations of two KDP crystals are discussed in detail. Using two 1.4-cm-thick type-II KDP tandem crystals, an overall energy efficiency higher than 60% was obtained in our experiment with the incident intensity ranging from 0.33GW/cm2 to 0.67GW/cm2. The laser beam had a diameter of 42mm. The experimetal results were in agreement with theoretical calculations. The measured performance of the tandem doubler (L1 = L2 = 1.4cm) was compared with those of simple crystal doublers with thicknesses of 3 cm and 1.4 cm respectively. The tandem doubler was found to have a combined merit of both the thick crystal doubler and the thin crystal doubler.