Electro-optical modulators are designed to modulate a light signal, i.e. they modulate on the characteristics of a light beam (such as its wavelength, polarization state or intensity) to encode a signal. The gap plasmon based modulators are the smallest existing modulators. Losses are reduced thanks to this small size. They operate over a large frequency range. Actually, the upper frequency limit of such devices is currently beyond the reach of electronic measuring devices.