A spectral filter (150.1-150.4) comprising at least one metallic layer (101) structured by at least one hole (250.1-250.4) passing through two opposite mains faces of the metallic layer and comprising, in a plane parallel to a plane of one of the two main faces, a first rectangular section whereof a first side has a dimension between around 40 nm and 100 nm, and whereof a second side, perpendicular to the first side, has a dimension between around 150 nm and 1000 nm, and a second rectangular section centered relative to the first rectangular section, a first side of the second section being parallel to the second side of the first section and having a dimension between around 40 nm and 100 nm.