The invention relates to an illumination device and a method adapted for illuminating applications. The illumination device (5) with a phosphor (1) comprising at least one light emitting surface which is adapted for emitting phosphor light in a predefined solid angle, a light source (2) being adapted for emitting optical radiation directed to the phosphor (1), a waveguide (3), and a reflector (4), wherein the phosphor (1) is optically coupled to the waveguide (3), the exit surface of the illumination device (5) from which light is emitted is larger than any single light emitting surface of the phosphor (1), and the reflector (4) is adapted for reflecting at least a part of the optical radiation emitted from the illumination device (5) by a surface different from the exit surface of the illumination device (5). In this way, a high light extraction efficiency from a single surface of a luminescent material and at the same time a high quantum efficiency of the illumination device is achieved.