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通过测量铌酸锂(LN)单模波导在不同波长下的半波电压,结合半波电压与电光重叠积分因子的依赖关系,实验发现了LN单模波导电光重叠积分因子随波长增大而迅速减小.另一方面,通过数值求解法分别得出了LN单模波导在不同波长的导模场分布和调制电场分布以及二者的重叠积分因子,在理论上获得了与实验数据十分近似的结果.进一步的仿真分析指出LN单模波导电光重叠积分因子随波长增大而减小的规律主要来自于导模的光场中心随波长增大逐渐远离波导表面,向低电场强度区域靠近.这种电光重叠积分因子的波长依赖特性是导致LN波导半波电压随波长增大而非线性上升的原因之一,它将为基于LN波导的器件的设计和优化提供重要参考.
By measuring the half-wave voltage of the single-mode waveguide of lithium niobate (LN) at different wavelengths and the dependence of half-wave voltage on the integral factor of electro-optical overlap, we found that the integral factor of electro-optical overlap of LN single-mode waveguide increases rapidly with the wavelength On the other hand, numerical simulation results show that the guided mode field distribution and modulated electric field distribution of LN single-mode waveguide at different wavelengths and their overlapping integral factors are theoretically obtained and are in good agreement with the experimental data Results The further simulations show that the law of the decrease of the integral factor of electro-optical overlap of LN single-mode waveguide with increasing wavelength mainly comes from the fact that the center of the light field moves away from the surface of the waveguide as the wavelength increases, and approaches the low-field intensity region. The wavelength dependence of the integral factor of electro-optical overlap is one of the reasons that the half-wave voltage of LN waveguide increases nonlinearly with the increase of wavelength. It will provide an important reference for the design and optimization of LN waveguide based devices.