金属光子晶体薄膜可见光和微波波段传输性能

一维金属光子晶体薄膜是由金属-介质多层结构组成的等效均匀的各向异性超构材料。相比单层金属膜层，该结构在色散调控方面具有更多的自由度。在该结构中由于表面等离子体激元(SPP)的存在，可实现倏逝波的定向传输。在本文中，等效介质理论、时域有限元差分法(FDTD)的计算结果和实验结果都表明，传输倏逝波的波长、频宽和强度可通过金属光子晶体结构调整实现主动设计。金属膜厚比例越小，传输波长的中心和截止波长越长，频带越宽。当金属膜层厚度小于SPP穿透深度时，可获得宽频段的倏逝波的传输。同时，对金属光子晶体在微波波段的传输性能也进行了研究，发现其在微波波段等效介电常数为负，具有良好的反射性能。该结构的屏蔽效能远大于厚度相近的ITO薄膜的电磁屏蔽效能。在厚度只有几百纳米时，该结构即可实现良好的电磁屏蔽效能。通过金属光子晶体薄膜可实现电磁屏蔽材料的薄膜化、轻质化和可视化。

Transmission properties of metal photonic crystal films in visible light and microwave

The one-dimensional metallic photonic crystal film is an anisotropic metamaterial with an equivalent and uniform metal-medium multilayered structure. Compared with the single-layer metal film, the one-dimensional metal photonic crystal film has a higher degree of freedom in terms of chromatic dispersion regulation and control. With the existing of surface plasmon polariton (SPP), directional transmission of evanescent waves can be achieved. The experimental results and the calculated results of the equivalent medium theory and the finite-difference time domain (FDTD) method show that the active control on the wavelength, bandwidth and strength of the evanescent waves during transmitting can be realized by regulating the metal photonic crystal structure. The smaller is the ratio of metal film thickness, the longer are the center of the transmission wavelength and the cutoff wavelength, and the wider is the frequency band. When the thickness of the metal film layer is smaller than the penetration depth of the SPP, wide frequency-band evanescent waves can be transmitted. This paper also studied the transmission performance in the microwave band of the metal photonic crystal, finding that at the microwave band, the equivalent dielectric constant of the metal photonic crystal is negative and the metallic photonic crystal has a good reflection property. Furthermore, the shielding effectiveness of the metal photonic crystal film is far better than the electromagnetic shielding effectiveness of the ITO film with the same thickness. Even at the thickness of a few hundred of nanometers, the metallic photonic crystal film can achieve good electromagnetic shielding effectiveness. Thus, by adopting the metallic photonic crystal film, light and visual electromagnetic shielding materials with thin films can be created.