对垂直多腔F-P规整膜系进行了结构上的划分,以反射膜系、腔层、耦合层为单位将膜系划分为若干个结构单元,利用史密斯方法将结构分为A、B两个系统。改变内膜系单元参数,得到了两腔F-P结构A、B系统反射率变化规律;改变A、B反射率的曲线交点和相位正弦值零点的位置,分析了透射曲线平顶响应的形成原因,得到了影响平顶响应薄膜滤波器性能参数的因素。得出透射性能良好的三半波膜系结构。其0.5 dB带宽为0.52 nm,3 dB带宽为0.67 nm,25 dB带宽为1.59 nm,矩形度为2.37(小于3)。

In this paper, the vertical multi-cavity film stack is divided into system A and B by using Smith method, and each part is composed of coating unit including reflection layers, cavity layers and coupling layers. By changing the coating unit parameters, the reflective variations of system A and B are obtained after coating units parameters are changed in two-cavity F-P structure. By changing the intersections of the reflectivity curves and the zero points of the half-phase sine value, the causes of flat top response characteristic are analyzed. The factors which impact the performance of flat-top thin film filter are obtained. At last, a three half film structure is designed which has the good performance. Its 0.5 dB bandwidths is 0.52 nm, 3 dB bandwidth is 0.67 nm, and 25 dB bandwidth is 1.59 nm, the rectangular factor is 2.37.