In 1962,N.Bloembergen,J.A.Armstrong and Yariv had successively putforward the quasi-phase matching theory.The theory anticipated that the se-cond harmonic effect may be in creased with a big margian on the basis of aperiodic sudden change in nonlinear coefficients.It also anticipated that some In 1962, N. Bloembergen, JAArmstrong and Yariv had successively put forward the quasi-phase matching theory. The theory now that the se-cond harmonic effect may be in creased with a big margian on the basis of aperiodic sudden change in nonlinear coefficients. It also anticipated that some