Abstract
Coordinated theoretical and experimental investigations were made of the conditions for achieving high
energy exchange in three-wave parametric interaction of temporally and spatially modulated picosecond
light packets. An efficiency of 
50% was achieved for conversion of pump energy into radiation with
continuously tunable wavelengths under optimal conditions in a KDP crystal. In this case, a spatial
pump-radiation profile without random amplitude-phase distortions was an extremely important factor.