基于改进PSO算法设计的TFLN平台偏振不敏感光栅耦合器

Polarization-insensitive grating coupler designed for TFLN platform based on improved PSO algorithm

针对光栅耦合器存在偏振依赖性问题,在薄膜铌酸锂(TFLN)平台上相继设计了标准型和改进型偏振不敏感光栅耦合器。在设计过程中,首先对粒子群(PSO)算法进行了改进,然后利用改进后的PSO算法对光栅参数进行了优化,包括光栅周期、占空比、刻蚀深度以及入射角等关键参数。最后,设计了偏振不敏感啁啾光栅耦合器,并通过线性啁啾调节有效折射率,从而显著提升了耦合效率和偏振不敏感带宽。仿真结果表明:在波长为1 544 nm时耦合效率最高,偏振不敏感啁啾光栅耦合器的横电(TE)、横磁(TM)模式耦合损耗分别为-4.88、-5.05 dB;在1 500~1 580 nm波长内偏振相关损耗(PDL)小于0.5 dB,偏振不敏感带宽为45 nm。

Aming at the polarization-dependency issue of grating couplers,standard and improved polarization-insensitive grating couplers are successively designed on the thin film lithium niobate(TFLN)platform.During the design process,the particle swarm optimization(PSO)algorithm is first improved,and then the improved PSO algorithm is used to optimize the grating parameters,including critical parameters such as grating period,duty cycle,etching depth,and incident angle.Finally,a polarization-insensi-tive chirped grating coupler is designed,and the effective refractive index is adjusted through linear chirp,significantly improving the coupling efficiency and polarization-insensitive bandwidth.The simulation results show that the coupling efficiency is the highest at the wavelength of 1544 nm,and the coupling losses of the transverse electric(TE)and transverse magnetic(TM)modes of the polarization-insensitive chirped grating coupler are-4.88 and-5.05 dB,respectively.The polarization-dependent loss(PDL)is less than 0.5 dB within the wavelength range of 1500 nm to 1580 nm,and the polarization-insensitive bandwidth is 45 nm.