An optical coupler in a vertical configuration, capable of working for a wavelength and comprising: - a first waveguide extending in the longitudinal direction and capable of propagating a first propagation mode of the light having a first effective index, - a second waveguide distinct from the first waveguide, parallel to the first waveguide, having a core and a cladding and capable of propagating a second propagation mode of the light having a second effective index, the second effective index being different from the first effective index, the optical coupler including a substrate, made from a first material, in which the second waveguide is buried, the first waveguide being arranged in contact with the substrate and formed from a material different from the first material, the second waveguide having a patterning, the patterning being in the form of a series of patterns, the patterns extending along a transverse direction perpendicular to the longitudinal direction, being parallel to each other and orthogonal to the general direction of the first waveguide, the optical coupler being characterized in that the patterning has a period along the longitudinal direction below the ratio between the wavelength at which the optical coupler is capable of operating and the product of two by the second effective index, each pattern is arranged both in the core and the cladding of the second waveguide, each pattern having parameters influencing the evanescent wave coupling between the first waveguide and the second waveguide at the wavelength at which the optical coupler is capable of operating, said parameters being chosen such that the coupling is greater than 15%. - a first waveguide extending in the longitudinal direction and capable of propagating a first propagation mode of the light having a first effective index, - a second waveguide distinct from the first waveguide, parallel to the first waveguide, having a core and a cladding and capable of propagating a second propagation mode of the light having a second effective index, the second effective index being different from the first effective index, the optical coupler including a substrate, made from a first material, in which the second waveguide is buried, the first waveguide being arranged in contact with the substrate and formed from a material different from the first material, the second waveguide having a patterning, the patterning being in the form of a series of patterns, the patterns extending along a transverse direction perpendicular to the longitudinal direction, being parallel to each other and orthogonal to the general direction of the first waveguide, the optical coupler being characterized in that the patterning has a period along the longitudinal direction below the ratio between the wavelength at which the optical coupler is capable of operating and the product of two by the second effective index, each pattern is arranged both in the core and the cladding of the second waveguide, each pattern having parameters influencing the evanescent wave coupling between the first waveguide and the second waveguide at the wavelength at which the optical coupler is capable of operating, said parameters being chosen such that the coupling is greater than 15%.