Research on wavefront properties of high power frequency tripling lasers based on type II/II KDP crystals

The relationship between the output frequency tripling (3ω) wavefront and the input fundamental laser (1ω) wavefront is researched in theory and experiment in the frequency conversion process based on type II/II KDP (KH2PO4) crystals. Theoretical results show the output 3ω wavefront distortion is three times of the input 1ω wavefront distortion on the phase-matching condition. The output 3ω and 1ω wavefront are measured by Hartman wavefront sensor in the high power frequency tripling laser system. Experimental results show that the output 3ω wavefront PV value is 2.97 times of the 1ω wavefront value and the output 3ω wavefront RMS value is 3.57 times of the 1ω wavefront value. Therefore, the theoretical relationship between the output 3ω wavefront and the input 1ω wavefront in the frequency conversion system is proved correct within the range of permitted experimental errors.