A plasmonic-effect optical security component, said component being able to be inspected with the naked eye, in reflection, via at least a first observation face (100 A), and comprising: - at least one first transparent layer of dielectric material, having a first refractive index (n 1), - at least one second layer of dielectric material, transparent, having a second refractive index, and said second layer of dielectric material making contact with said first layer of dielectric material; - a metal layer making contact with said at least one second layer of dielectric material; wherein: - said first layer of dielectric material, said second layer of dielectric material and said metal layer form a first dielectric-dielectric-metal double interface that comprises a first dielectric-dielectric interface and a first dielectric-metal interface, and that is structured to form, in at least one first coupling region (Z 1), a first two-dimensional coupling grating (C 1), with a first direction and a second direction, having a first period (p x) comprised between 150 nm and 350 nm in the first direction and a second period (p y) comprised between 150 nm and 350 nm in the second direction, - said first coupling grating (C 1) is determined so as to generate a first plasmon-resonance effect at said at least one first dielectric-metal interface in a first resonance spectral band, wherein the optical security component is characterized in that: - the thickness of the at least one second layer of dielectric material is comprised between 20 nm and 150 nm, - the difference between the second refractive index and the first refractive index is larger than or equal to 0.5, and in that - the thickness of said at least one second layer of dielectric material is determined so as to generate, by means of said first coupling grating (C 1), a hybrid plasmon-resonance effect, in a second resonance spectral band different from said first spectral band. - at least one first transparent layer of dielectric material, having a first refractive index (n 1), - at least one second layer of dielectric material, transparent, having a second refractive index, and said second layer of dielectric material making contact with said first layer of dielectric material; - a metal layer making contact with said at least one second layer of dielectric material; wherein: - said first layer of dielectric material, said second layer of dielectric material and said metal layer form a first dielectric-dielectric-metal double interface that comprises a first dielectric-dielectric interface and a first dielectric-metal interface, and that is structured to form, in at least one first coupling region (Z 1), a first two-dimensional coupling grating (C 1), with a first direction and a second direction, having a first period (p x) comprised between 150 nm and 350 nm in the first direction and a second period (p y) comprised between 150 nm and 350 nm in the second direction, - said first coupling grating (C 1) is determined so as to generate a first plasmon-resonance effect at said at least one first dielectric-metal interface in a first resonance spectral band, wherein the optical security component is characterized in that: - the thickness of the at least one second layer of dielectric material is comprised between 20 nm and 150 nm, - the difference between the second refractive index and the first refractive index is larger than or equal to 0.5, and in that - the thickness of said at least one second layer of dielectric material is determined so as to generate, by means of said first coupling grating (C 1), a hybrid plasmon-resonance effect, in a second resonance spectral band different from said first spectral band.