Patent Number: 
Section: claims

1. A method of making an electro-optic window having reduced RF and microwave transmission characteristics, the method comprising:providing a window that is formed from a material that is substantially transparent to at least one of infra-red, visible and UV radiation;forming on a surface of the window a grid of channels;sputtering over the surface of the window a layer of a material having one of electrically conductive and dielectric properties to substantially fill the channels of the grid;selectively etching the surface of the window, thereby removing the sputtered material from the surface while leaving the channels of the grid substantially filled with the material, creating a corresponding grid pattern of the material within the channels, and thereby rendering the window non transmissive to RF/MICROWAVE radiation; andtreating the material as required to render the grid usable to reduce the RF/MICROWAVE transmission characteristics of the window. 2. The method according to claim 1, wherein the material is a metal. 3. The method according to claim 1, wherein the step of forming on a surface of the window a grid of channels comprises forming the grid of channels by laser etching the window material. 4. The method according to claim 1, wherein the step of forming on a surface of the window a grid of channels comprises forming the grid of channels by chemically etching the window material. 5. The method according to claim 1, wherein the step of forming on a surface of the window a grid of channels comprises:forming a mould in the shape of an EO window, the mould defining a positive grid formation whereby to impart to a moulded window a negative grid formation on one surface of the window;forming a sol of a material suitable for sintering and pouring the sol into the mould;converting the sol to a gel by the application of heat;drying the gel whereby to impart to the gel a permanent shape corresponding to that of the mould; andvitrifying the gel by sintering whereby to form a sintered EO window having the grid of channels formed on one surface thereof. 6. The method according to claim 1, further comprising a step of forming a capping layer configured to cover the grid and attach to the window surface by:forming a mould;forming a sol and pouring the sol into the mould;converting the sol to a gel by the application of heat;drying the gel whereby to impart to the gel a permanent shape reflecting that of the mould; andvitrifying the gel by sintering whereby to form a said capping layer.