[en] Experimental investigation into a maximum efficiency of radiation energy conversion of multicascade neodymium lasers in KDR crystals in the second, third and fourth harmonics is conducted for the purpose of laser heating of a hermonuclear plasma. The efficiency of laser radiation energy conversion to the second harmonics = 90%, to the third one = 80% has been experimentally obtained. Attaining the efficiency of radiation energy conversion of the second harmonics to the fourth one, being equal to 93%, points to the reality of using the given process in experiments on laser fusion