Abstract
A formulation of the theory on the noncollinearly phase matched second harmonic generation is given. The theory treats the effects of phase mismatching and of the interaction volume of two differently directed fundamental laser beams. When the crystal is rotated from the matching angle, the second harmonic power decreases more rapidly with the enlargement of the interaction volume. The experimental results suggest the validity of the theory. Comparison with the collinear case indicates that higher power can be obtained in the noncollinear case.