周期结构薄膜在折射率色散下反射区特性研究

周期性结构是光学薄膜设计的基本物理模型,给出了反射区中心波长的一般性条件,研究了在膜层材料存在折射率色散情况下,等厚周期结构和非等厚周期结构的薄膜反射区中心波长与带宽特性.研究结果表明:在等厚和非等厚周期结构中,考虑膜层材料折射率色散与忽略色散情况相比,中心波长向长波方向移动,反射级次与相对波数的线性关系偏离;在薄膜光学厚度一定的非等厚周期结构中,高折射率层光学厚度大于低折射率层时,反射级次与相对波数的线性关系偏离度高;非等厚周期结构薄膜的带宽在低反射级次上小于等厚周期结构,同时膜层的色散对反射带宽影响不大.

Properties of reflecting region of periodic-structured thin film with refractive index dispersion

Periodic structure is the basic physical model in optical film design. Universal conditions of the reflecting center wavelength are given. With the refractive index dispersion of the layers, the reflecting center wavelength and the band characteristic of equal-thickness and unequal-thickness periodic structures are studied. According to experimental results, in both the equal-thickness and unequal-thickness periodic structures with the refractive index dispersion of the coating layers, the reflecting center wavelength moves towards the longer wavelengths, and the reflective series as well as the relative wave number will depart from linear relation. For the same optical thickness of the film with unequal-thickness periodic structure, when the optical thickness of the high refractive index layer is bigger than that of the low refractive index layer, the departure from linear relation between the reflective series and the relative wave number is higher. For the low reflective series, the bandwidth of unequal-thickness periodic structure is smaller than that of equal-thickness periodic structure. The influence of the layer dispersion on the bandwidth is found to be weak.