Transmission peculiarities of dielectric layer/thin metallic film/dielec-tric layer structure, with or without periodicity in the dielectric layers

摘要

The transmission characteristics of the dielectric grating - thin metal film - dielectric grating structure have been analyzed by the coupled wave method (CWM). The analysis is conducted for waves of TE and TM polarizations. The qualitative transmission characters are similar for two polarizations, but are different quantitatively. The reflectance of such structure can be higher than 0.85 on wavelength of 1.5um at certain parameters for a silver film with thickness of 0.0385μm. The reflectance on the wavelength of the maximum transmission is actually equal to zero. The only thin film without gratings on the same wavelength has the transmittance of 0.004 and reflectance of 0.984. The system, which consists of grating from metal included between homogeneous dielectrics, also possesses by anomalous high transmission. At that the transmission is substantially higher than a ratio of a metal-free space to the grating period. Similar dependences can be obtained for a structure, in which the thin film of metal is located between two layers of dielectric with high refraction index. At certain conditions the reflection is less than 0.0002 and transmission is more than 0.87 for the metal thickness of 0.0385 μm. The rule is found, which is enable to find approximately the parameters for these high transmission structures. This effect is explained by the coupled wave resonance with forming of a wave node within the thin metal film that minimizes absorption.