A multicrystal means of compensating for the thermally induced phase mismat
ch encountered in the generation of high average power UV radiation is desc
ribed. The concept is experimentally tested with a Nd:YAG laser 4th harmoni
c generator based on two beta-BaB2O4 (BBO) crystals. Single versus two crys
tal results demonstrate that this design compensates for the thermally indu
ced phase mismatch, effectively increasing the interaction length of nonlin
ear optical crystals during harmonic generation under high loading. (C) 200
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