An on-chip broadband radiation source comprising - at least one optical waveguide (101, 902) comprising a core (101, 902) and a cladding material (102, 903), - a III-V membrane, forming an LED structure, the III-V membrane having a thickness between λ/20 ∗ n1 and λ/2 ∗ n1, where λ is the operating wavelength and n1 the geometric average refractive index of the III-V membrane material, the III-V membrane being positioned on top of the optical waveguide (101, 902), and there being a refractive index contrast such that n1-n0>1, with n0 being the refractive index of an upper (5, 105) or a lower (2, 3, 6, 101, 102) cladding material surrounding the III-V membrane at least in a direction perpendicular to the membrane, the lower cladding material corresponding to the at least one optical waveguide (101, 102, 902, 903), wherein, if the upper (5, 105) or the lower (2, 3, 6, 101, 102) cladding material consists of different layers, the refractive index n0 corresponds with an average refractive index, averaged over the different layers wherein the at least one optical waveguide or the III-V membrane comprises a coupling means for transferring an optical pump signal from the optical waveguide up to the III-V membrane wherein the coupling means is a taper or a grating, and wherein the III-V membrane has an absorption capability for absorbing the optical pump signal transferred up to the III-V membrane so as to pump the LED structure thus inducing broadband radiation at a wavelength longer than the wavelength of the optical pump signal, and the emitted signal from the LED structure is coupled back into the waveguide. - at least one optical waveguide (101, 902) comprising a core (101, 902) and a cladding material (102, 903), - a III-V membrane, forming an LED structure, the III-V membrane having a thickness between λ/20 ∗ n1 and λ/2 ∗ n1, where λ is the operating wavelength and n1 the geometric average refractive index of the III-V membrane material, the III-V membrane being positioned on top of the optical waveguide (101, 902), and there being a refractive index contrast such that n1-n0>1, with n0 being the refractive index of an upper (5, 105) or a lower (2, 3, 6, 101, 102) cladding material surrounding the III-V membrane at least in a direction perpendicular to the membrane, the lower cladding material corresponding to the at least one optical waveguide (101, 102, 902, 903), wherein, if the upper (5, 105) or the lower (2, 3, 6, 101, 102) cladding material consists of different layers, the refractive index n0 corresponds with an average refractive index, averaged over the different layers wherein the at least one optical waveguide or the III-V membrane comprises a coupling means for transferring an optical pump signal from the optical waveguide up to the III-V membrane wherein the coupling means is a taper or a grating, and wherein the III-V membrane has an absorption capability for absorbing the optical pump signal transferred up to the III-V membrane so as to pump the LED structure thus inducing broadband radiation at a wavelength longer than the wavelength of the optical pump signal, and the emitted signal from the LED structure is coupled back into the waveguide.