Electromagnetic shielding design and thin film preparation of large-aperture Ge infrared window

The relationship between the diffraction distribution of random metal mesh mesh and the linewidth of the mesh was analyzed by theoretical calculation and FDTD Solutions software simulation. A random-structure metal mesh electromagnetic shielding film with a line width of 5 μm was prepared on a large-aperture germanium optical window by mask vacuum lithography and electron beam evaporation coating technology, and then the infrared dual-band anti-reflection coating and DLC protective film were coated by electron beam evaporation and PECVD on the germanium window, respectively. Furthermore, the transmittance in the infrared band and electromagnetic shielding effectiveness in the microwave band of the window were characterized. The results show that the windows coated with random-structure metal meshs, anti-reflection coatings and DLC films have excellent electromagnetic shielding effectiveness in the frequency range of 1GHz~18GHz, and have high transmittance in the 3.5μm~4.5μm and 7.5μm~9.5μm bands.