| CPC G02B 1/118 (2013.01) [G02B 1/12 (2013.01); G02B 5/0808 (2013.01); G02B 5/208 (2013.01)] | 15 Claims |

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1. An optical device, suitable for transmitting/reflecting electromagnetic radiation in a wavelength range of an electromagnetic spectrum, said device comprising:
a substrate made of a first material chosen from the following materials:
silicon Si, germanium Ge, zinc sulphide ZnS, zinc selenide ZnSe,
a coating layer formed on a first side of the substrate and made of a second material, different from the first material, this second material being chosen from the following materials: silicon Si, germanium Ge, zinc sulphide ZnS, zinc selenide ZnSe, tantalum pentoxide Ta2O5, hafnium dioxide HfO2, alumina Al2O3,
at least a rear layer formed on a second side of the substrate opposed to the first side and having an optical function different from the coating layer, said rear layer being made of a material different from the substrate and from the coating layer, and
a surface having a plurality of cavities formed by surface texturing in a pattern forming a varying effective refraction index,
wherein the plurality of cavities are extending through the coating layer and are partially sunk into the substrate,
wherein the optical device is suitable for transmitting/reflecting electromagnetic radiation in a wavelength range of the electromagnetic spectrum corresponding to an infrared radiation,
wherein the material of the rear layer is a member of a group consisting of: silicon Si, germanium Ge, zinc sulphide ZnS, and zinc selenide ZnSe.
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