The invention provides a light generating system (1000) comprising a light generating device (100), a luminescent body (200), and first optics (410), wherein: •the light generating device (100) is configured to generate device light (101); wherein the light generating device (100) comprises a laser; •the luminescent body (200) comprises a luminescent material (210), wherein the luminescent material (210) is configured to convert at least part of the device light (101) into luminescent material light (211), and wherein the luminescent body (200) is transmissive for at least part of the luminescent material light (211); •the first optics (410) are transmissive for at least part of the device light (101) and reflective for at least part of the luminescent material light (211), wherein the first optics (410) comprise a primary optic surface (411) having a first surface area A1, wherein the primary optic surface (411) is configured in a light receiving relationship with the light generating device (100); •the luminescent body (200) is enclosed by a cavity (500) having a cavity opening (510) having a smallest cross-sectional area A2, wherein the cavity (500) is at least partly defined by the optics (410); wherein the first optics (410) comprises the cavity opening (510); wherein A2