Optical filtering device including Fabry-Perot cavities and structured layer belonging conjointly to first and second interference filters

An optical filtering device, comprising:

• at least first and second interference filters each comprising at least one first Fabry-Perot cavity formed by first and second semi-reflective layers between which at least one first structured layer is arranged, wherein
• the first structured layer belongs conjointly to the first and second interference filters, has a substantially constant thickness, is substantially planar and comprises first portions of at least two dielectric or semiconductor materials, with different refractive indices, arranged, in each of the first Fabry-Perot cavities and in a plane parallel to the first semi-reflective layer, alongside one another in alternation,
• the first Fabry-Perot cavity of the second interference filter comprises at least one first spacer arranged between one of the first and second semi-reflective layers and the first structured layer in such a way that a distance between the first and second semi-reflective layers of the first Fabry-Perot cavity of the second interference filter is greater than a distance between the first and second semi-reflective layers of the first Fabry-Perot cavity of the first interference filter, and
• the first and second interference filters are produced such that:
• the first and second interference filters each comprise at least one second Fabry-Perot cavity placed on top of the first Fabry-Perot cavity and formed by the first and a third semi-reflective layer between which at least one second structured layer is arranged, the second structured layer belonging conjointly to the first and second interference filters, having a substantially constant thickness, being substantially planar and comprising second portions of the two materials with different refractive indices arranged, in each of the second Fabry-Perot cavities and in the plane parallel to the first semi-reflective layer, alongside one another in alternation, the second Fabry-Perot cavity of the second interference filter further comprising at least one second spacer arranged between the third semi-reflective layer and the second structured layer so that a distance between the first and third semi-reflective layers of the second Fabry-Perot cavity of the second interference filter is greater than a distance between the first and third semi-reflective layers of the second Fabry-Perot cavity of the first interference filter, and the second structured layer is arranged above the first structured layer.

A method for producing an optical filtering device comprising at least first and second interference filters each comprising at least one first Fabry-Perot cavity, the method comprising:

• producing a first semi-reflective layer of the first Fabry-Perot cavities;
• producing, on the first semi-reflective layer, a first structured layer belonging conjointly to the first and second interference filters, having a substantially constant thickness, being substantially planar and comprising first portions of at least two dielectric or semiconductor materials, with different refractive indices, intended to be arranged, in at least one of the first Fabry-Perot cavities and in a plane parallel to the first semi-reflective layer, alongside one another in alternation;
• producing at least one first spacer at a region of the first structured layer intended to form part of the first Fabry-Perot cavity of the second interference filter;
• and
• producing a second semi-reflective layer of the first Fabry-Perot cavities, wherein
• a distance between the first and second semi-reflective layers of the first Fabry-Perot cavity of the second interference filter being greater than a distance between the first and second semi-reflective layers of the first Fabry-Perot cavity of the first interference filter,
• the first and second interference filters are produced so that:
• the method further comprises, before the first semi-reflective layer is produced, the production of at least one second Fabry-Perot cavity of each of the first and second interference filters, superimposed on the first Fabry-Perot cavity and formed by the first and a third semi-reflective layers between at least one second structured layer is produced, the second structured layer belonging conjointly to the first and second inference filters, having a substantially constant thickness, being substantially planar and comprising second portions of the two materials with different refractive indices arranged, in at least one of the second Fabry-Perot cavities and in the plane parallel to the first semi-reflective layer, alongside one another in alternation, the second Fabry-Perot cavity of the second interference filter further comprising at least one second spacer arranged between the third semi-reflective layer and the second structured layer so that a distance between the first and third semi-reflective layers of the second Fabry-Perot cavity of the second interference filter is greater than a distance between the first and third semi-reflective layers of the second Fabry-Perot cavity of the first interference filter, and
• a plurality of said first interference filters are made alongside one another and wherein proportions by volume of the two materials with different refractive indices with respect to each other, in at least one of the first structured layer and the second structured layer, are different from one first interference filter to the other, or wherein a plurality of said second interference filters are made alongside one another and wherein proportions by volume of the two materials with different refractive indices with respect to each other in at least one of the first structured layer and the second structured layer, are different from one second interference filter to the other.