A light conversion system comprising (a) one or more luminescent bodies , (b) a thermally conductive body , (c) a waveguide element , and (d) a light generating device , wherein: - the thermally conductive body comprises a first reflective face , and a first slit in at least part of the first reflective face , wherein the first slit comprises a first slit opening ; - the waveguide element comprises a light entrance part and a light exit part , wherein at least part of the light exit part is configured in the first slit ; wherein the waveguide element is configured to guide at least part of first light coupled into the waveguide element via the light entrance part to the light exit part ; - the one or more luminescent bodies comprise a reflector-directed part and a optical output part ; wherein the reflector-directed part is in thermal contact with at least part of the first reflective face and wherein the reflector-directed part encloses at least part of the first slit opening ; wherein the one or more luminescent bodies are configured (a) to receive via at least part of the reflector-directed part at least part of the first light escaping from the light exit part of the waveguide element and (b) to convert in a light conversion process at least part of the first light into luminescent material light , wherein at least part of the luminescent material light emanates from the optical output part ; and - the light generating device is configured to generate the first light , wherein the light generating device is configured upstream of the light entrance part of the waveguide element ; and wherein the light generating device comprises a solid-state light source. - the thermally conductive body comprises a first reflective face , and a first slit in at least part of the first reflective face , wherein the first slit comprises a first slit opening ; - the waveguide element comprises a light entrance part and a light exit part , wherein at least part of the light exit part is configured in the first slit ; wherein the waveguide element is configured to guide at least part of first light coupled into the waveguide element via the light entrance part to the light exit part ; - the one or more luminescent bodies comprise a reflector-directed part and a optical output part ; wherein the reflector-directed part is in thermal contact with at least part of the first reflective face and wherein the reflector-directed part encloses at least part of the first slit opening ; wherein the one or more luminescent bodies are configured (a) to receive via at least part of the reflector-directed part at least part of the first light escaping from the light exit part of the waveguide element and (b) to convert in a light conversion process at least part of the first light into luminescent material light , wherein at least part of the luminescent material light emanates from the optical output part ; and - the light generating device is configured to generate the first light , wherein the light generating device is configured upstream of the light entrance part of the waveguide element ; and wherein the light generating device comprises a solid-state light source. <EOS>