Optical device comprising: - a waveguide , comprising a core having a refractive index n c , for guiding quasi-monochromatic light radiation, of a central wavelength λ, in a propagated mode with effective index n eff , in a first direction A and transmitting said radiation through an exit facet of the waveguide to the external environment with effective index n 0 at the central wavelength λ, n 0 being different from n eff , according to a transmission coefficient T, the exit facet being substantially perpendicular to the first direction A, the optical device being further characterised in that it further comprises: - a filter blade , with effective index n s at the central wavelength λ, n s being different from n eff , advantageously an air blade, arranged in the waveguide , parallel to the exit facet and at a first non-zero distance e slab from said exit facet , the filter blade having, in the first direction A, a first non-zero thickness e slit , the first distance e slab and the first thickness e slit being adapted so that the transmission coefficient T of the waveguide is equal to a first transmission coefficient T 1 for the propagated mode with effective index n eff at the central wavelength λ, the first transmission coefficient T 1 being the ratio between the intensity of the propagated mode transmitted by the facet and the intensity of the propagated mode incident on the filter blade, the first transmission coefficient T 1 being greater than a transmission coefficient T d of the waveguide devoid of any filter blade , T d being the ratio between the intensity of the propagated mode transmitted by the facet and the intensity of the propagated mode incident on the facet. - a waveguide , comprising a core having a refractive index n c , for guiding quasi-monochromatic light radiation, of a central wavelength λ, in a propagated mode with effective index n eff , in a first direction A and transmitting said radiation through an exit facet of the waveguide to the external environment with effective index n 0 at the central wavelength λ, n 0 being different from n eff , according to a transmission coefficient T, the exit facet being substantially perpendicular to the first direction A, - a filter blade , with effective index n s at the central wavelength λ, n s being different from n eff , advantageously an air blade, arranged in the waveguide , parallel to the exit facet and at a first non-zero distance e slab from said exit facet , the filter blade having, in the first direction A, a first non-zero thickness e slit , the first distance e slab and the first thickness e slit being adapted so that the transmission coefficient T of the waveguide is equal to a first transmission coefficient T 1 for the propagated mode with effective index n eff at the central wavelength λ, the first transmission coefficient T 1 being the ratio between the intensity of the propagated mode transmitted by the facet and the intensity of the propagated mode incident on the filter blade, the first transmission coefficient T 1 being greater than a transmission coefficient T d of the waveguide devoid of any filter blade , T d being the ratio between the intensity of the propagated mode transmitted by the facet and the intensity of the propagated mode incident on the facet. <EOS>