Optical structure for localising an electromagnetic field and detector or emitter device including such a structure

Device including at least one active optical member provided in a medium of positive dielectric permeability and, in the proximity of said active member, an optical structure including a layer of a material of negative dielectric permeability, said layer having, located in an orthogonal reference frame 0xyz, a surface having a relief y=h(x,z) invariant along 0z and variable along 0x, the 0y axis being oriented from the positive dielectric permeability medium to said layer of negative dielectric permeability, said surface contacting said positive dielectric permeability medium and including a first relief area, having a profile in 0xy cross section that includes a periodic repetition of a unit pattern and a second relief area symmetrical to said first area with respect to a plane of symmetry parallel to 0yz, said first and second areas being separated by a third layer provided in the centre of the structure, giving rise, compared with said first and second areas, to a fault in periodicity of the relief surface, wherein said unit pattern is defined by four succeeding portions, a first portion of full width at half maximum a and a second portion of full width at half maximum b, a third portion of full width at half maximum c and a fourth portion of full width at half maximum d, said first and third portions having substantially the same height ht, said second and fourth portions having substantially the same height hd different from ht, with ht strictly higher than hd and in that a, b, c, d and hg=ht−hd are selected profile parameters such that:

• each of them is not zero,
• the sum a+b+c+d is equal to the period Λ and
• at least a≠c or b≠d.