Preparation and optical-microwave performance of metal photonic crystals

Metal photonic crystals (MPCs), which combine the optical properties of metals with photonic crystals, can effectively control and restrain the propagation of light at sub-wavelength scale, there many peculiar optical transmission phenomena are exhibited for MPCs. When the metal film thickness in MPCs is less than the surface plasmon polaritons (SPPs) penetration depth, the bulk plasmon polaritons (BPPs) propagating in three-dimensional space are formed for tunneling effect and SPP coupling. This enables visible light, which could not be transmitted in metals to transmit well in MPCs. The central wavelength, the frequency width and the intensity of transmission wave are designed and adjusted actively by designing proper structure, such as the material properties, the film thickness ratio of metal and dielectric, the period as well as the periodic numbers. In addition, MPCs have strong electromagnetic shielding ability for the negative effective permittivity in infrared, radio and microwave ranges. MPCs can be compatible with wide band electromagnetic shielding effectiveness (SE) and good visual ability.

    Zhao Yali Senior Engineer Research Team of China Electronic Technology Group Corporation thirty-third Research Institute and Li Xufeng Associate Professor Team of Taiyuan University of Science and Technology are dedicated to the study of the visible and microwave spectral characteristics of MPCs.
    By using equivalent medium, photonic crystal Bragg scattering and SPP coupling theory, the effects of MPCs’ structure on optical characteristics was revealed. MPCs with excellent photoelectric properties were prepared by optimizing the deposition temperature, the oxygen-to-argon ratios and annealing process. The transmission and reflection characteristics of MPCs are actively and effectively designed and controlled by designing a suitable structure. They have developed a metal photonic crystal consisting of metal Ag and ITO film, which was compatible with wide band electromagnetic shielding and good optical transparency. It is the SE of MPCs that is obviously better than that of ITO film, and the visual sense is also obviously better than that of metal mesh structure. Compared with metal composite films, an active design of the transmitted frequencies and the color sense of optical window was realized. It opens new possibilities for visual color design and optical filter production with MPCs.. 
    In addition, the teams have also proposed a MPCs with discontinuous metal film. It has a low square resistance of 0.53 Ω, a good conductivity that is very close to a metal microgrid. The half bandwidth of visible transmittance of which is between 380nm and 780nm, such MPCs can enhance both the resolution and the response rate of the flat panel display. In addition, the structure design of metal photonic crystal can also be used to enhance the reflection of different bands of visible light. Figs. 1-3 are the reflections of photonic crystals with ITO film thickness of 60, 80 and 120 nm, respectively.

Fig.1  Optical reflection spectra simulated using FDTD for normal incidence with 3.5 pairs of Ag/ITO, consisting of Ag with thicknesses from 8 nm to 22nm, and a fixed ITO thickness of 60 nm. 

Fig.2  Optical reflection spectra simulated using FDTD for normal incidence with 3.5 pairs of Ag/ITO with a Ag layer ranging from 8 nm to 22 nm thickness and fixed ITO thickness of 80 nm. 
Fig.3  Optical reflection spectra simulated using FDTD for normal incidence with 3.5 pairs of Ag/ITO with a Ag layer ranging from 8 nm to 22 nm and ITO films of 120 nm thickness.

About Team
The team of Zhao Yali Senior Engineer from Shanxi Key Laboratory of Electromagnetic Protection Technology, NO.33 Research Institute of China Electronics Technology Group and Li Xufeng, Associate Professor, School of Applied Sciences, Taiyuan University of Science and Technology is mainly engaged in the research on the design and application of metamaterials. In recent years, they have undertaken the research projects of National Defense 863 and Chinese Defense advance program of science and technology and so on. The team is devoted to the research of design and application of metamaterials. The contraction between electromagnetic shielding and optical transparency, electromagnetic absorption and optical transparency, high conductivity and optical transparency have been solved by adopting metamaterials. Nowadays, nearly 40 papers have been published and co-published in this field. One monograph has been compiled. The team has won the second prize for scientific and technological progress in Shanxi Province, the second prize for science and technology and the third prize for science and technology in China Electronic Science and Technology Group Corporation, and the first prize and the second Prize for technological innovation in national defense science and technology industry in Shanxi Province.

Zhao Yali, Li Xufeng, Jia Kun, et al. Optical characteristics of one dimensional metal-dielectric photonic band gap material[J]. Opto-Electronic Engineering, 2018, 45(11): 180239.