摘要
采用了耦合波理论对结构尺度远小于波长的二维亚波长周期光栅进行了讨论，结果表明，这种二维亚波长光栅可等效成一介质层，这介质层具有双折射晶体的性质，文中给出了相应的等效折射率，在此基础上我们采用数值计算的方法分析了在不同人射角情况下该介质层的反射特性，从而给出了抗反膜的设计参数．
Film coating is currently used to produce antireflective surfaces. Alternatively, a high-spatial- frequency grating on a substrate can behave as an antireflection surface. This is an interesting alternative because of problems concerned. For example, high-spatial-frequency grating is frequently used to avoid potential performance degradation caused by the elevated temperatures usually raquired for optical coating. The coupled-wave theory may be adopted to analyze grating diffraction. When light is incident to the grating, its unit cell scale is comparable to light wave length. Because of grating diffraction, transmission and reflective waves include many diffraction order which are coupled with each other. So the analytic solution of reflectivity can not be given and reflectivity can not be Changed with the incident light wave on this condition. In this article, the planar sub wavelength periodical grating is discussed. The results show all the diffraction order can not exist except the zeroth diffraction order and reflectivity does not change with the wavelength of incident light wave. Considering the condition that incident plane include the grating vector and n3 = 1. 5 or n3 = 2, reflective characteristics of this kind of medium layer are analyzed by numerical computation. The variation in the reflectivity of TM wave (RTE) corresponding to RTM = 0 when n3 = 1. 5 or n3 = 2 is plotted as a function of the incident angle in Fig. 3. When the incident angle is in the range of 0°-40° at n3 = 1. 5, RTE<0. 01 A peak can be discovered near the angle of 56°. When the incident angle is in the range of 0°-32° at n3 =2,RTE<0. 01,a peak can be discovered near the angle of 56'. The antireflective film with good effects can be made in the angle range mentioned above. Fig. 4 is the relation curve between incident angle 4 and filling factor F tinder the condition of RTE = 0 at when n3 = 1. 5 or n3 = 2. Comparing Fig. 3 with Fig. 4, it can be observed that the peak in Fig. 3 is just at the Brewster angle. The research presented above indicates that the antireflective film with better effects can be fabricated in the range of 00-400 Under the following conditions: (1) n3 = 1. 5; (2) the incident plane includes the grating vector.
出处
《南京大学学报（自然科学版）》
CAS
CSCD
北大核心
2001年第1期56-62,共7页
Journal of Nanjing University（Natural Science）
基金
江苏省自然科学基金!(BK99048)
关键词
深亚波长位相光栅
抗反射
双折射
光学元件
deep sub-wavelength periodical grating, antireflective, birefractive
