论文部分内容阅读
基于有限元算法建立用于刻写中红外光纤布喇格光栅(Fiber Bragg Grating,FBG)的相位模板物理模型,对相位模板的衍射光场进行模拟分析。在模拟过程中,采用平面波和球面波两种不同光源。采用平面波作为入射光时,通过改变平面波的入射角度和相位模板光栅的刻槽深度分析Talbot衍射图样的变化。采用球面波作为入射光时,通过改变光源与相位模板的距离分析衍射图样的变化。结果表明,当平面波以任意角度斜入射时,沿与入射光相同方向形成Talbot衍射图样。当改变相位模板刻槽深度时,Talbot衍射图样的形状和能量分布均发生变化:随着刻槽深度的增加,衍射能量最大值逐渐变大;当刻槽超过一定深度时,能量最大值开始减小,同时Talbot图像向均匀条纹演变。当球面波入射到相位模板时,Talbot衍射图样沿球面波传播方向分布。随着球面波波源逐渐靠近相位模板,能量最大值逐渐升高;当超过一定距离时,能量最大值开始下降。
Based on the finite element method, a physical model of the phase mask for writing a middle-infrared fiber Bragg grating (FBG) is established, and the diffraction field of the phase mask is simulated. In the simulation process, using plane wave and spherical wave two different light sources. When using plane wave as incident light, the change of Talbot diffraction pattern is analyzed by changing the incident angle of plane wave and the groove depth of phase grating. When spherical waves are used as incident light, the change of the diffraction pattern is analyzed by changing the distance between the light source and the phase mask. The results show that the Talbot diffraction pattern is formed in the same direction as the incident light when the plane wave is obliquely incident at any angle. The shape and energy distribution of the Talbot diffraction pattern change when the depth of the phase template is changed: the maximum value of the diffraction energy becomes larger as the depth of the groove increases; when the depth of the groove exceeds a certain depth, the energy maximum begins to decrease Small, while Talbot images evolve toward uniform stripes. When the spherical wave is incident on the phase mask, the Talbot diffraction pattern is distributed along the spherical wave propagation direction. As the spherical wave source gradually approaches the phase mask, the maximum energy gradually increases; when it exceeds a certain distance, the maximum energy begins to decrease.