SINGLE-SIDED ILLUMINATION OF HIGH LUMEN DENSITY LAMPS

The invention provides a lighting system (1) comprising: - a light source (10) configured to provide light source light (11); - an elongated luminescent body (100) having a length (L), the elongated luminescent body (100) comprising: - a plurality of side faces (140) over at least part of the length (L), wherein the side faces (140) comprise a first side face (143), comprising a radiation input face (111), and a second side face (144) configured parallel to the first side face (143), wherein the side faces (143, 144) define a height (H), wherein the elongated luminescent body (100) further comprises a radiation exit window (112) bridging at least part of the height (H) between the first side face (143) and the second side face (144); - a garnet type A3B5O12 luminescent material (120) comprising trivalent cerium, with a height dependent concentration selected from a concentration range defined by a minimum concentration ymin = 0.036*x-1 and a maximum concentration ymax = 0.17*x-1, wherein y is the trivalent ce