基于多光束干涉原理, 从高斯光束在自由空间的传输方程出发, 推导了高斯光束斜入射角度调谐窄带滤光片的反射光强以及透射光强的表达式。在此基础上研究了滤光片入射角对高斯光束反射特性的影响和关系。理论数值计算和实验结果都表明, 随着入射角度的增大, 滤光片透射光强的光斑会出现明显的展宽现象, 而其反射光强的光斑虽会在较大角度斜入射时出现一定的展宽, 但是展宽幅度远小于透射光斑的变化。故角度调谐窄带滤光片的反射端口在其调制范围内不需要跟透射端口一样进行光斑整形处理。

Based on the multi-beam interference principle and Gaussian beam transmission equation in the free space, the intensity expression of a Gaussian beam incidenting obliquely on an angle-tuned narrowband filter has been derived. According to the result, the influence and relationship of the incident angle on the reflection of a Gaussian beam have been investigated theoretically. The calculation and experiment results show that the size of the transmitting beam spot will be brodened obviously when the incident angle is increasing. However, the size of reflecting beam spot will be a little brodened for a relatively large incident angle, which extent is much less than that of the transmitting beam. The reflecting port of the angle-tuned narrowband filter does not need facular-shaping fitting as the transmitting port within its tuanble range.