A lighting device comprising: - a light source configured to provide light source light; - a luminescent element comprising an elongated light transmissive body, the elongated light transmissive body comprising a side face, wherein: - the elongated light transmissive body comprises a luminescent material configured to convert at least part of a light source light selected from one or more of ultraviolet light, visible light, and infrared light received by the elongated light transmissive body into luminescent material radiation; - the side face comprises a curvature with a radius r; - wherein the elongated light transmissive body comprises a radiation input face and a first radiation exit window; wherein the luminescent material is configured to convert at least part of light source light received at the radiation input face into luminescent material radiation, and the luminescent element being configured to guide at least part of the luminescent material radiation to the first radiation exit window by total internal reflection and to couple at least part of the luminescent material radiation out at the first radiation exit window as converter radiation; - wherein the elongated light transmissive body has a first face and a second face defining a length of the elongated light transmissive body; wherein the side face comprises the radiation input face, wherein the second face comprises the radiation exit window, - characterized in that the concentration of the luminescent material is chosen such that at least 80% of the light source light is absorbed within a first length x from the side face, wherein x/r≤0.4 applies. - a light source configured to provide light source light; - a luminescent element comprising an elongated light transmissive body, the elongated light transmissive body comprising a side face, wherein: - the elongated light transmissive body comprises a luminescent material configured to convert at least part of a light source light selected from one or more of ultraviolet light, visible light, and infrared light received by the elongated light transmissive body into luminescent material radiation; - the side face comprises a curvature with a radius r; - wherein the elongated light transmissive body comprises a radiation input face and a first radiation exit window; wherein the luminescent material is configured to convert at least part of light source light received at the radiation input face into luminescent material radiation, and the luminescent element being configured to guide at least part of the luminescent material radiation to the first radiation exit window by total internal reflection and to couple at least part of the luminescent material radiation out at the first radiation exit window as converter radiation; - wherein the elongated light transmissive body has a first face and a second face defining a length of the elongated light transmissive body; wherein the side face comprises the radiation input face, wherein the second face comprises the radiation exit window, - characterized in that the concentration of the luminescent material is chosen such that at least 80% of the light source light is absorbed within a first length x from the side face, wherein x/r≤0.4 applies.