设计了一种新的光路结构,用于提高LiNbO3波导相位调制器的偏振消光比。光路特点是,在质子交换波导3 dB功分器的输入端同基构造了TiLiNbO3波导模式分离定向耦合的结构以实现TE导模与TM模分离,Y分支波导位置下沉以避免前向TM辐射模的窜扰。效果表现为,与保偏光纤端耦合寄生的TM辐射模得到了有效抑制,寄生的TM导模被定向疏散。1 550 nm波长的BPM仿真运行表明,设计光路的偏振消光比达到87 dB以上。

A new optical structure is designed to improve the polarization extinction ratio of LiNbO3 waveguide phase modulator.At the input of the 3 dB power divider of the proton exchange waveguide,there is a Ti-LiNbO3 waveguide mode separation directional coupler with the base structure for the separation of TE mode and TM mode.Y-branch waveguide is sunk to avoid scrambling of the forward TM radiation mode.The parasitic TM radiation mode with polarization-maintaining fiber is effectively suppressed and the parasitic TM guided mode is evacuated.The BPM simulation of 1 550 nm wavelength shows that the polarization extinction ratio of the designed optical path is more than 87 dB.