Structure for extracting a guided mode

A structure for extracting a guided mode of wavelength λ, linearly polarized along a polarization direction, comprising:

• a support substrate 100 comprising a substantially flat upper face,
• a main waveguide configured to guide the guided mode,
• an intermediate waveguide configured to guide a so-called coupled mode, at the wavelength λ, comprising a liquid crystal core extending parallel to the upper face, and an output face, the core extending to the output face,
• a flat surface facing the output face, reflective at the wavelength λ, making a non-zero angle with the upper face of the support substrate,
• a first electrode and a second electrode, arranged with respect to the core of the intermediate waveguide so as to switch, in a coupling portion of the core of the intermediate waveguide, a refractive index of the liquid crystal, along the polarization direction, from a first level to a second level, when a variation of an electrical potential difference is applied between the first and the second electrodes,
• wherein the first level, the second level, and the arrangement of the coupling portion with respect to the main waveguide is such that the guided mode, when it is present, is at least partially coupled, by evanescent coupling from the main waveguide to the coupling portion only when the refractive index of the coupling portion is equal to the second level.