A method for precise adjustment of the power splitting ratio for integrated optical splitters fabricated on lithium niobate substrates is proposed. The method is based on a local refractive index change caused by the photorefractive effect under external illumination of certain areas of waveguide power splitters. A fiber optic probe was used for precise positioning of an external illumination spot. Predictable tuning of the splitting ratio for two basic splitter configurations (directional couplers and y-branches) was demonstrated. Precise adjustment of the power splitting ratio in a relatively narrow range (2%) led to a significant growth in the Mach–Zehnder modulator extinction ratio (as high as 17 dB, from 30 to 47 dB). The proposed method is simple and can prove to be a very promising additive technique for improvement of lithium niobate integrated optical schemes.

中文翻译：

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光折变效应局部激发对铌酸锂基片集成光功分器的精确校正

提出了一种精确调整铌酸锂基片上集成分光器功率分光比的方法。该方法基于波导功率分配器的某些区域在外部照射下由光折变效应引起的局部折射率变化。光纤探头用于精确定位外部照明点。演示了两种基本分路器配置（定向耦合器和 y 分支）的分路比的可预测调整。在相对较窄的范围 (2%) 内精确调整功率分配比导致 Mach-Zehnder 调制器消光比的显着增长（高达 17 dB，从 30 到 47 dB）。