An optical structure enabling properties of the surface plasmons to be used is defined from a substantially binary, parameterizable unit pattern ME. The parameters a, b, c, d and h.sub.g of the pattern are chosen so as to maximize the complex amplitudes of the first two harmonics of the complex Fourier series describing the pattern ME. This structure is advantageously used in combination with a photodetector, an infrared or Terahertz optical wave emitter, or a field emission device.