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We propose the idea of using a grating structure for solving the problem of the incomplete quasi-phase matching (QPM) period and demonstrate the simulation results of phase compensation in achieving efficient round-trip optical parametric oscillation in periodically poled LiNbO/sub 3/ (PPLN). The layout of a monolithic optical parametric oscillator (OPO) with two surface gratings at both ends is shown. The two gratings are chirped to guarantee that their phase variations over the Bragg reflection windows are larger than 2/spl pi/. One of them has a length of 1 mm and the other has a length of 0.8 mm. The pump input is applied from the long grating side and the signal output is obtained from the short grating side. The whole PPLN length is 5 mm. For our numerical study, we consider the pump wavelength at 1064 nm and signal wavelength at 1550 nm. The idler wavelength is hence at 3.393 /spl mu/m. The corresponding QPM period of PPLN is 29.6 /spl mu/m. The central grating period is 361.83 nm, which corresponds to the Bragg wavelength 1550 nm. To obtain numerical results, we solved the coupled equations for the forward and backward pump complex amplitudes, the forward and backward signal complex amplitudes, and the forward and backward idler complex amplitudes.