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A novel model of two-dimensional periodically poled lithium niobate designed for second harmonic generation of 1064 nm is proposed, in which a rectangular light route is used. The effective length of the sample is longer than the sample real length by (5/3).21/2 times. The conversion efficiency enhances greatly without prolonging the periodically poled crystal length.

The effect of LiNbO3 electrode with three different configurations o n domain broadening by using poling method appling external electric field applying exter nal electric field is studied. The effect of poling electrode configuration in d omain broadening is studied. The experiment demonstrated that under the same pol ing condition, the broadening velocities are 0.089μm/ms and 0.011μm/ms when th e angle between the poling electrode and the diagonals of hexagonal domain nucl eus are 90°and 0°，respectively, therefore the circumstance of 90°angle betwe en poling electrode and the diagonals of hexagonal domain nucleus should be avoi ded in fabricating one-dimension nonlinear photonic crystal.

The high-order collinear and non-collinear quasi-phase matching harmonic generations were realized in a two-dimensional periodically poled LiNbO3 wit h square lattice by tuning the input wavelength. The output spots lay at different symme tric positions with respect to the input beam of picosecond pulse, and the relat ive intensities of spots at certain wavelengths were measured. The high-order no nlinear harmonic processes were also realized by tuning the input angle. The exp erimental and theoretical results are in good agreement with each other. Our stu dies might be beneficial to the development of optics integration and compact de vices.

A two-dimensional periodically poled lithium niobate crystal with a 13.64 μm period was fabricated. The inverted duty cycle was about 23%. The second harmonic output for the second-order quasi-phase-matching (QPM) against the input was measured. The maximum second harmonic internal conversion efficiency was higher than 40%. All results implied that the second-order QPM could be used to obtain high-frequency conversion efficiency. Compared with the first-order QPM, the second-order QPM can reduce the requirement for the poling technique and the mask fabrication.