Study on the Mechanism of Defect Introduction in Waveguide Gratings

为了研究波导光栅在引入缺陷时所产生的影响，丰富硅基集成器件参数的调控机制，通过有限时域差分法，仿真分析了波导光栅分别在引入对称和非对称米氏散射体结构形成缺陷时所造成的影响。仿真结果表明：对于对称的米氏散射体，槽刻蚀的深度控制反射的幅度，深度越大，反射越强，当其为200 μm时反射率达到0.0268，但需注意避免槽刻蚀深度过大导致导波模式损耗；对于非对称米氏散射体，透射率较高，峰值为0.8561，槽刻蚀深度所造成的影响与对称米氏散射体类似，但是会导致缺陷左右两侧r1和r2的反射系数不同，引入非互易耦合。此类具有可控缺陷结构的波导光栅为新型硅基集成器件开发提供了多功能平台，可提升高灵敏度传感器检测极限等关键性能指标，并拓展片上功能元件的应用场景。In order to study the effect of introducing defects in waveguide gratings and extend the reference range of design parameters of silicon-based integrated devices, the effects of introducing defects in symmetric and asymmetric Mie scatterers are simulated and analyzed by finite-difference time-domain method. The simulation results show that the depth of the groove etch controls the amplitude of reflection for symmetric Mie scatterers. The greater the depth, the stronger the reflection. When the depth reaches 200μm, the reflectance is 0.0268, but attention should be paid to avoid the loss of guided wave mode caused by excessive groove etch depth. For asymmetric Mie scatterers, the transmittance is high, with a peak value of 0.8561. The effect of groove etching depth is similar to that of symmetric Mie scatterers, but the reflection coefficients of r1 and r2 on the left and right sides of the defect are different, and non-reciprocal coupling is introduced. The influence of different structural defects can provide a design basis for terahertz communication and high-sensitivity sensors.