非线性波导是一种重要的光量子器件。采用马卡梯里近似, 可以近似描述波导的模场分布特征。针对ee-e准相位匹配的周期极化铌酸锂波导, 分析波长为1 064 nm的基波和 532 nm的 二次谐波的基模模场分布。结果表明: 如果波导为嵌入型正方形波导, 基波和二次谐波的光斑基本为圆形, 基波场分布范围较大; 在截面正方形边长为5 μm并且芯区比包层折射率略高002时, 波导就能将两种光波场基本约束在芯区中, 但是这种波导边长为05 μm时约束能力就变得很差; 如果采用芯区与包层折射率差别较大的波导, 芯区边长为05 μm就可以将两种场分布基本约束在芯区中。结果对分析其他类型的非线性波导的模场分布具有指导意义。

Nonlinear waveguide is an important photon quantum device. Using Marcatili approximation, mode field distribution characteristics of waveguide can be approximately described. For periodically poled LiNbO3 waveguide with ee-e quasi-phase matching, fundamental mode field distribution of fundamental wave with a wavelength of 1 064 nm and second harmonic of 532 nm is analyzed. Results show that if waveguide is an embedded square waveguide, fundamental and second harmonic are basically circular, and range of fundamental wave field is larger. When length of square side of section is 5 μm and core area is slightly 0.02 higher than cladding refractive index, waveguide can basically confine two kinds of light field in core region, but constraint ability becomes very poor when waveguide length is 0.5 μm. If difference between core region and cladding layer is large, waveguide with 0.5 μm side length can get two kinds of field distribution constrained in core area basically. Results are of significance to analysis of modes of other types of nonlinear waveguides.