System for guiding a beam of electromagnetic radiation

A system for guiding a beam of electromagnetic radiation, the beam including a vacuum wavelength, the system comprising:

• at least a first stack of dielectric layers;
• and
• at least one electromagnetic generating layer generating the beam of electromagnetic radiation, the electromagnetic generating layer being outside of the first stack of layers, at least a part of the beam being guided in the first stack of dielectric layers, the first stack comprising:
• a first substack, the first substack including at least one dielectric layer;
• a second substack, the second substack including at least one dielectric layer;
• and
• a third substack, the third substack including at least one dielectric layer, the third substack separating the first and second substack,
• wherein dielectric layers of the first substack and the second substack equidistant from the third substack have the same refractive index,
• wherein the sum of the thickness of dielectric layers of the first substack and the second substack being equidistant from the third substack is a multiple of half of the vacuum wavelength of the beam divided by the refractive index of the dielectric layers of the first substack and the second substack being equidistant from the third substack,
• wherein the third substack thickness is substantially different from a quarter of the vacuum wavelength of the beam divided by the refractive index of the dielectric layer of the third substack, and
• wherein the first substack and the second substack each have an odd number of layers and comprise dielectric layers with refractive indices n1 and n2;
• and
• wherein said:
• refractive indices n1 and n2 are different in value relative to each other, such that the equivalent penetration depth of said beam is negative.