缓冲质子源LiNbO3波导折射率计算及实验

为实现铌酸锂退火质子交换(APE)波导折射率分布的准确计算,选择含苯甲酸锂的苯甲酸缓冲液作为质子交换质子源,高温退火制作了波导样本.针对该工艺过程建立退火质子交换波导模型,包括非线性扩散模块和光学数值仿真模块,分别计算APE波导折射率及其模式有效折射率.以测得的样本波导模式有效折射率和计算的有效折射率差的均方根构建评价函数(FOM),结合遗传算法提取该工艺条件下质子扩散参数,实现了不同交换深度和退火时间波导折射率分布及其光学特性的一体化计算.实验表明:FOM小于0.001,计算折射率分布同IWKB方法测得结果吻合较好,最大偏差约0.002.

Calculation and Experimental Demonstration of Waveguide Refractive Index of LiNbO3 Fabricated by Buffered Proton Source

In order to accurately calculate the refractive index profile of the annealed proton-exchanged (APE) lithium niobate waveguide, the buffered benzoic acid with lithium benzoate is chosen as proton-exchanged (PE) source, and the APE waveguide samples are fabricated by the annealing process. The APE model including nonlinear diffusion module and optical numeric simulation module has been established to calculate the refractive index profile of the APE waveguide and its mode effective indices, respectively. The generic method with the help of the figure of metric (FOM) which is the mean square deviation between the calculated mode effective indices and the measured values of the APE waveguides is used to extract the diffusion parameters of proton, the refractive index profile and its effective indices of the waveguide with different proton-exchanged depths and annealing time can be calculated. The experiment results show that the FOMs are below 0.001 and the calculated refractive index profiles and the experimental inverse Wentzel-Kramers-Brillouin (IWKB) profiles are in good agreement with the maximum difference of ~0.002.