| 摘要 |
A bi-periodic grating comprises first zones 3 of a constituent material having a first electrical conductivity and second zones 4 made of complimentary material with a lower electrical conductivity. Both materials have similar complex indices of refraction, and they form a mechanically continuous layer. Preferably, the materials are formed from the same semiconducting material, and the zones are formed by using different concentration of the same dopant. Suitable materials include germanium doped with antimony, silicon doped with boron, phosphorous or arsenic, or gallium arsenide doped with silicon or selenium or tellurium. The grating allows the transmission of optical waves, while reflecting microwaves and absorbing radar. It may be used to faradise an optronic window with respect to at least one frequency band of the Hertzian wave domain.
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