An illumination device comprising: a plurality of solid state light sources and a concentrating wavelength converter arranged to inject light from said light sources through at least one entrance surface and to extract wavelength converted light from at least one exit surface, wherein said wavelength converter is configured to provide total internal reflection of converted light when an incidence angle at a side surface is between A and 90 degrees, where the angle A is determined by the refractive index of the converter and the surrounding media, respectively, and wherein the geometry of said wave length converter is such that an incidence angle of converted light at said exit surface, after total internal reflection in said side surface, is in a range including angles greater than A, whereby A is defined as A = asin (n surr / n conv) where n surr is the index of refraction of the surrounding media of the wavelength converter and where n conv is the index of refraction of the material forming the wavelength converter, a structured layer provided on said exit surface, characterized in that said structured layer has a structure period less than 5 micrometers, so as to enable out-coupling by a combination of refraction and diffraction, and in that the index of refraction of the material forming said structured layer is equal to or greater than n conv - 0.3, wherein said exit surface is normal to said side surface so that the incidence angle of converted light at said exit surface, after reflection in said side surface, is between zero and 90-A degrees, wherein the angle A is between 20 and 40 degrees. a plurality of solid state light sources and a concentrating wavelength converter arranged to inject light from said light sources through at least one entrance surface and to extract wavelength converted light from at least one exit surface, wherein said wavelength converter is configured to provide total internal reflection of converted light when an incidence angle at a side surface is between A and 90 degrees, where the angle A is determined by the refractive index of the converter and the surrounding media, respectively, and wherein the geometry of said wave length converter is such that an incidence angle of converted light at said exit surface, after total internal reflection in said side surface, is in a range including angles greater than A, whereby A is defined as A = asin (n surr / n conv) where n surr is the index of refraction of the surrounding media of the wavelength converter and where n conv is the index of refraction of the material forming the wavelength converter, a structured layer provided on said exit surface, characterized in that said structured layer has a structure period less than 5 micrometers, so as to enable out-coupling by a combination of refraction and diffraction, and in that the index of refraction of the material forming said structured layer is equal to or greater than n conv - 0.3, wherein said exit surface is normal to said side surface so that the incidence angle of converted light at said exit surface, after reflection in said side surface, is between zero and 90-A degrees, wherein the angle A is between 20 and 40 degrees.